I have two arrays. Array A and Array B. Now I need to get where in array B is sequence from array A located. I need to get location of last number and I don't know how.
A[4]={6,3,3,2};
B[10][18]={
{5,3,6,5,6,1,6,1,4,4,5,4,4,6,3,3,1,3},
{6,2,3,6,3,3,2,4,3,1,5,5,3,4,4,1,6,5},
{6,4,3,1,6,2,2,5,3,4,3,2,6,4,5,5,1,4},
{5,3,5,6,6,4,3,2,6,5,1,2,5,6,5,2,3,1},
{1,2,5,2,6,3,1,5,4,6,4,4,4,2,2,2,3,3},
{4,1,4,2,3,2,3,6,4,1,6,2,3,4,4,1,1,4},
{5,3,3,2,6,2,5,2,3,1,2,6,5,1,6,4,1,3},
{4,5,2,1,2,5,2,6,4,3,3,2,3,3,3,1,5,1},
{1,3,5,5,2,1,3,3,3,1,3,3,6,3,3,3,6,5},
{4,5,2,4,2,3,4,2,5,6,5,2,6,3,5,4,5,2}
};
For example: Sequence 6,3,3,2 start in second row and in forth column and ends in seventh column. I need to get location of number 2. My result should be:
Row = 2,
Column= 7
Sequence isn't always in row. It can be in column to. For example:
3,2,4,3 and I ned to know location of number 4.
I know how to search one number in one dimensional array but in this case I don't have solution.
Language is C.
You can compare blocks using memcmp:
for (i = 0; i < rows; i++) { /* For each row */
for (j = 0; j < cols - size; j++) { /* For each col until cols - 4 */
if (memcmp(A, &B[i][j], sizeof(A)) == 0) { /* Compare entire block */
#include <stdio.h>
#include <string.h>
int main(void)
{
int A[4] = {6,3,3,2};
int B[10][18] = {
{5,3,6,5,6,1,6,1,4,4,5,4,4,6,3,3,1,3},
{6,2,3,6,3,3,2,4,3,1,5,5,3,4,4,1,6,5},
{6,4,3,1,6,2,2,5,3,4,3,2,6,4,5,5,1,4},
{5,3,5,6,6,4,3,2,6,5,1,2,5,6,5,2,3,1},
{1,2,5,2,6,3,1,5,4,6,4,4,4,2,2,2,3,3},
{4,1,4,2,3,2,3,6,4,1,6,2,3,4,4,1,1,4},
{5,3,3,2,6,2,5,2,3,1,2,6,5,1,6,4,1,3},
{4,5,2,1,2,5,2,6,4,3,3,2,3,3,3,1,5,1},
{1,3,5,5,2,1,3,3,3,1,3,3,6,3,3,3,6,5},
{4,5,2,4,2,3,4,2,5,6,5,2,6,3,5,4,5,2}
};
size_t i, j, size, rows, cols;
int founded = 0;
size = sizeof(A) / sizeof(A[0]);
rows = sizeof(B) / sizeof(B[0]);
cols = sizeof(B[0]) / sizeof(B[0][0]);
for (i = 0; i < rows; i++) {
for (j = 0; j < cols - size; j++) {
if (memcmp(A, &B[i][j], sizeof(A)) == 0) {
founded = 1;
break;
}
}
if (founded) break;
}
if (founded) printf("Row: %zu Col: %zu\n", i + 1, j + size);
return 0;
}
The problem is not the language. The problem you face is you need to come out with the algorithm first.
Actually this can be easily done by just looking at the first number of the 1D array. In your example it is 6 from (6,3,3,2).
Look for 6 in your 2D array.
Once 6 is found use a loop which loop 4 times (because there are 4 numbers to look for - (6,3,3,2).
In the loop, check whether the subsequent numbers are 3,3,2.
If it is, return the location
Else continue the process to look for 6.
Done!
It will look like this:
for(x=0; x<rows; x++)
for(y=0; y<cols; y++)
{
if(matrix[x][y] == array1D[0])
for(z=1; z<array1DSize; z++){
if(matrix[x][y] != array1D[z])
break;
location = y;
}
}
If you know how to do it with a one dimensional array, you can do it like that in C with multidimensional arrays too!
For instance, say you have a two dimensional array like so:
int array[5][5]; // 5x5 array of ints
You can actually access it in linear fashion, by doing:
(*array)[linear offset]
So that means if you want to access the 2nd column of the 2nd row, you can do:
(*array)[6]
Because the 2nd row starts at index 5, and the second column is at index 1, so you would do (5+1) to get 6. Likewise, the 3rd row would start at index 10, so if you wanted the 2nd column in the third row, you can do (10+1).
Knowing that, you can take your original algorithm and adapt it to access the multidimensional array in a linear fashion. This takes place of the "wrap around" possibility as well.
Related
I was working on the following 2d-array program to output this result shown in picture:
I can't seem to get the min value for the result and get it displayed in array form.
The code is below:
#include<stdio.h>
#define NUMROWS 2
#define NUMCOLS 3
//accessing elements of 2D array using pointers
int main(void){
const int table[NUMROWS][NUMCOLS]={{1,2,3},{5,6,7}};
int minvals[NUMROWS];
int i, j;
int *ptr = &table;
//accessing the elements of 2D array using ptr
printf("table values: min value\n");
for(int i=0;i<NUMROWS;i++){
for(int j=0;j<NUMCOLS;j++)
printf("%d ",*((ptr+i*NUMCOLS)+j));
printf("\n");
}
for(int i=0;i<NUMROWS;i++){
for(int j=0;j<NUMCOLS;j++)
printf("%d ",*((ptr+i*NUMCOLS)+j)<minvals[i]);
}
return 0;
}
The existence of minvals would imply that you are expected to calculate the minimum value of each 'row' of table before then moving on to printing. As it stands, had your program properly calculated the minimum values of each array, your printing would be rather out of order.
There's no need to do any tricky, manual pointer manipulation. Simple array subscription is much clearer.
Let's start simple and return to basics by looking at the way we find the minimum value in a one dimensional array, as it is the core of this problem.
To find the minimum value in an array we need a few things to start:
An array
The length of the array
An initial value to compare against
The array itself is obviously each subarray of table, and the length in this case is known to be NUMCOLS. Our initial value should either be INT_MAX (or another type-appropriate maximum constant found <limits.h>), such that every element in the array is equal to or less than our initial value, or a value from the array itself.
Often times we opt for the second option here, choosing the first element in the array as our initial value, and comparing it to the second and onward elements.
As such, finding the minimum value in a single 'row' would look like this
const int row[NUMCOLS] = { 9, 2, 5 };
int min = row[0];
for (int i = 1; i < NUMCOLS; i++)
if (row[i] < min)
min = row[i];
but since we want to find and record the minimum value of each 'row' in table, we're going to use a nested loop. Instead of the min variable from before, we store each value in the associated index of our minvals array.
for (i = 0; i < NUMROWS; i++) {
minvals[i] = table[i][0];
for (j = 1; j < NUMCOLS; j++)
if (table[i][j] < minvals[i])
minvals[i] = table[i][j];
}
When it comes time to print, we're going to repeat our nested loop. Our inner loop prints each element of each 'row' of table, and we end each iteration of the outer loop by printing the value found in minvals with the same index of our 'row'.
for (i = 0; i < NUMROWS; i++) {
for (j = 0; j < NUMCOLS; j++)
printf("%6d", table[i][j]);
printf(":%6d\n", minvals[i]);
}
Here's a working example.
#include <stdio.h>
#define NUMROWS 2
#define NUMCOLS 3
int main(void) {
const int table[NUMROWS][NUMCOLS] = {
{ 9, 2, 5 },
{ 3, -4, -12 }
};
int minvals[NUMROWS];
int i, j;
for (i = 0; i < NUMROWS; i++) {
minvals[i] = table[i][0];
for (j = 1; j < NUMCOLS; j++)
if (table[i][j] < minvals[i])
minvals[i] = table[i][j];
}
puts("Table value: minimum values");
for (i = 0; i < NUMROWS; i++) {
for (j = 0; j < NUMCOLS; j++)
printf("%6d", table[i][j]);
printf(":%6d\n", minvals[i]);
}
}
A good further exercise for you would be to compose the logic of the inner loop for finding minimum values into a more generic function. Its function signature would look like
int min(int *array, size_t length);
allowing it to work on arrays of varying sizes. Then our outer loop could be as simple as:
for (i = 0; i < NUMROWS; i++)
minvals[i] = min(table[i], NUMCOLS);
The line
int *ptr = &table;
is wrong, because &table is of type int (*)[2][3] (i.e. a pointer to the entire table), whereas ptr is a pointer to a single element. Also, your pointer is non-const, so it cannot point be made to point into a const array.
If you want ptr to point to a single int value, then you should declare it the following way:
const int *ptr = &table[0][0];
Also, you are reading the contents of the array minvals, although that array contains uninitialized data. This does not make sense and causes undefined behavior.
Instead of doing complex pointer arithmetic with the expression
*((ptr+i*NUMCOLS)+j))
you can simply write the following:
table[i][j]
That way, you do not need the pointer ptr and your code is simpler.
Im stuck with a piece of my Arduino code
Basically I have a multi dimensional array in which every index will store a random letter. But after a small time (eg. 900 milliseconds) every value in the index will move up to the index above it. Ofcourse when the index reaches e.g. [9][0] it will go to the largest index like [9][9]
E.g.: myArray[9][8] contains "K" and myArray[9][7] contains "L"
The "K" in myArray[9][8] will be put in myArray[9][7] and the "L" in myArray[9][7] will go to myArray[9][6] etc. etc
But I have no clue how to do this in C...
myArray[9][8] = myArray[9][7] obviously wouldnt work
There is not problem with assignment, but you must save the element you are writing over first.
In this example all the rewritten values are kept in the last slot of every row, this is just an example- not the only way to go, if you need to move the letters across the rows as well the idea is similar.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
void moveLettersInRow(char sArr[][3], int row)
{
int i = 0;
int j = 0;
char temp ;
for (i = 0; i < row; ++i)
{
for(j = 2 ;j > 0;--j)
{
temp = sArr[i][j-1]; /*save the value to be rewritten */
sArr[i][j-1]= sArr[i][2]; /* set the last val in its new place*/
sArr[i][2]= temp; /* set the last elem to the latest rewritten value*/
}
}
}
void printArr(char arr[][3], int size)
{
int i = 0, j= 0;
for(i = 0; i< size; ++i)
{
for(j = 0; j< 3; ++j)
{
printf("%c | ", arr[i][j]);
}
printf("\n");
}
}
int main()
{
char arr[2][3]= {{'a','b','c'},{'a','b','c'}};
moveLettersInRow(arr, 2);
printArr(arr, 2);
return 0;
}
There are several ways to go about this. One would be to use a temporary variable while copying, as Kami Cuk and Fred pointed out.
Another way, which would avoid copying the values, would be to index the array using a modulo operation while reading the array.
myArray[9][(index + offset) % numberOfElementsInArray]
index and offset should both be positive integers.
numberOfElementsInArray is the number of elements in myArray[9]
To get a -1 offset with a positive integer, set offset to numberOfElementsInArray - 1
I created an array called elements_n which has the elements 0 to N-1 where N is 2. The below numbers are the elements of the array called elements_n:
0 1
I have another array called Arr which has the following elements:
0 1 3 1 2 4
If any of the first 3 elements of the array Arr are equal to the first element of elements_n which is 0, I would like to delete that element from the array called Arr. I then repeat the same process for the next 3 elements of the array Arr. So to explain myself better, I will use the following example:
Compare the first 3 elements of array Arr which are 0, 1, 3 to the first element of elements_n which is 0. Since Arr[0] == elements_n[0]. I delete Arr[0] from the array Arr.
Compare the next 3 elements of array Arr which are 1, 2, 4 to the second element of elements_n which is 1. Since Arr[3] == elements_n[1]. I delete Arr[3] from the array Arr. So the elements that should be left in the array Arr are:
1 3 2 4
When I implemented it myself in C programming with the code found below the end result is coming:
1 3 3 2 2 4
Rather than:
1 3 2 4
This is the code I implemented:
#include <stdio.h>
#include <stdlib.h>
#define N 2
int main() {
unsigned *elements_n = malloc(N * sizeof(unsigned));
for (int i = 0; i < N; i++) {
elements_n[i] = i; //Created an array which has the elements 0 to N-1
}
printf("\n");
unsigned Arr[6] = { 0, 1, 3, 1, 2, 4 };
unsigned position_indices[2] = { 3, 3 }; //Moving every 3 elements in the Arr array.
int count = 0;
int index = 0;
unsigned *ptr_Arr = &Arr[0];
do {
for (int i = 0; i < position_indices[count]; i++) {
if (ptr_Arr[i] == elements_n[count]) {
index = i + 1; //Index of the Arr element that has the same value as the element in the array elements_n
for (int j = index - 1; j < position_indices[count] - 1; j++) {
ptr_Arr[j] = ptr_Arr[j + 1];
}
}
}
printf("\n");
ptr_Arr += position_indices[count] - 1;
count++;
} while (count < 2);
for (int i = 0; i < 6; i++) {
printf("%d\t", Arr[i]);
}
printf("\n");
free(elements_n);
return 0;
}
You might try something like this (not tested).
#include <stdio.h>
#include <stdlib.h>
#define N 2
int main()
{
unsigned *elements_n = malloc(N * sizeof(unsigned));
for (int i = 0; i < N; i++)
{
elements_n[i] = i; //Created an array which has the elements 0 to N-1
}
unsigned Arr[6] = { 0, 1, 3, 1, 2, 4 };
int dest_index = 0;
int src_index = 0;
int count = sizeof(Arr)/sizeof(Arr[0]);
for ( ; src_index < count; src_index++)
{
int group = src_index / 3;
if (Arr[src_index] != elements_n[group])
{
Arr[dest_index++] = Arr[src_index];
}
}
for (int i = 0; i < dest_index; i++)
{
printf("%d\t", Arr[i]);
}
printf("\n");
free(elements_n);
return 0;
}
You need to keep track of how many elements you removed from the array.
My solution:
#include <stdio.h>
#include <stddef.h>
#include <assert.h>
#include <string.h>
size_t fancy_delete_3(const int elems[], size_t elemssize, int arr[], size_t arrsize)
{
assert(elems != NULL);
assert(arr != NULL);
assert(arrsize%3 == 0);
assert(elemssize*3 == arrsize);
// we need to count the removed elements, to know how much we need to shift left
size_t removed = 0;
// for each element in elems
for (size_t i = 0; i < elemssize; ++i) {
// check the three correponding elements in arr
for (size_t j = i*3; j < (i+1)*3; ++j) {
assert(j >= removed);
const size_t pos = j - removed;
// if elems[i] matches any of the corresponding element in arr
if (elems[i] == arr[pos]) {
// remove element at position pos
assert(arrsize >= pos + 1);
// I don't think this can ever overflow
memmove(&arr[pos], &arr[pos + 1], (arrsize - pos - 1) * sizeof(int));
++removed;
// array is one element shorter, so we can just decrease the array size
assert(arrsize > 0);
--arrsize;
}
}
}
// we return the new size of the array
return arrsize;
}
#define __arraycount(x) sizeof(x)/sizeof(x[0])
int main()
{
int elements_n[] = {0,1};
int arr[] = {0,1,3, 1,2,4};
size_t newsize = fancy_delete_3(elements_n, __arraycount(elements_n), arr, __arraycount(arr));
printf("arr size=%zu {", newsize);
for (size_t i = 0; i < newsize; ++i)
printf("%d,", arr[i]);
printf("}\n");
return 0;
}
You have several related problems around how you perform deletions. In the first place, it's not clear that you understand that you cannot actually delete anything from a C array. The closest you can come is to overwrite it with something else. Often, pseudo-deletion from an array is implemented by moving each of the elements following the deleted one one position forward, and reducing the logical length of the array.* You seem to have chosen this alternative, but (problem 1) you miss maintaining or updating a logical array length.
Your problem is made a bit more complicated by the fact that you logically subdivide your array into segments, and you seem not to appreciate that your segments are variable-length in that, as described, they shrink when you delete an element. This follows from the fact that deleting an element from one group does not change the assignments of elements to other groups. You do have a mechanism in position_groups that apparently serves to track the sizes of the groups, and in that sense its name seems ill-fitting. In the same way that you need to track and update the logical length of the overall array, you'll need to track and update the lengths of the groups.
Finally, you appear to have an off-by-one error here:
for (int j = index - 1; j < position_indices[count]-1; j++)
that would be clearer if position_indices were better named (see above), but recognizing that what it actually contains is the size of each group, and that index and j represent indices within the group, it follows that the boundary condition for the iteration should instead be just j < position_indices[count]. That's moot, however, because you're going to need a somewhat different approach here anyway.
Suggestion, then:
When you delete an element from a group, move up the entire tail of the array, not just the tail of the group.
In service to that, update both group size and logical array size when you perform a deletion, remembering that that affects also where each subsequent group starts.
When you examine or output the result, remember to disregard array elements past the logical end of the array.
* "Logical array size" means the number of (leading) elements that contain meaningful data. In your case, the logical array size is initially the same as the physical array size, but each time you delete an element (and therefore move up the tail) you reduce the logical size by one.
You never really "deleted" any element, you just shifted-down the
second and third elements from each 3-group. And then, when
printing, you iterated over the whole array.
Arrays are just continuous blocks of memory, so you need a
different strategy. You could traverse the original array with
two indexes, one as the general index counter and other as
the index for the shifted slot. If the current element is
different from the corresponding elements_n item, copy it to
the secondary index and increase it.
In case nothing is equal to the elements_n item, you would just
reassign the array elements to themselves. However, as soon as
one is equal you will be shifting them with the advantage of
keeping track of the new size.
Also, calculating the corresponding elements_n item is a simple
matter of dividing the current index by 3, so you don't even need
an extra variable to that.
#include <stdio.h>
#define N 2
int main()
{
unsigned elements_n[N] = { 0, 1 };
unsigned Arr[N*3] = { 0, 1, 3, 1, 2, 4 };
int i, j;
for (i = 0, j = 0; i < N*3; i++)
if (Arr[i] != elements_n[i/3])
Arr[j++] = Arr[i];
for (i = 0; i < j; i++)
printf(" %d", Arr[i]);
printf("\n");
return 0;
}
I am successfully storing the calculated subsets in a 2-D array matrix in C language.Now I want to print the subsets in an order desired.
For eg.
2-D array matrix is
10 7 3 2 1
10 7 5 1
7 6 5 3 2
10 6 5 2
10 7 6
Desired Output
10 7 6
10 7 5 1
10 7 3 2 1
10 6 5 2
7 6 5 3 2
How quick sort can be applied to sort/order these rows?
As #chqrlie noted, this can be easily solved with qsort.
Depending on the way the matrix is declared (is it an array of pointers to arrays of ints? do all arrays have the same length? is it a global array of fixed size?) the code will have to do slightly different things.
So, assuming the array is a global variable and all rows have same length (padded with 0s):
MWE:
#include <stdio.h>
#include <stdlib.h>
/*
Compare 2 integers
returns:
-1 if *i1 < *i2
+1 if *i1 > *i2
0 if *i1 == *i2
*/
int intcmp(const int *i1, const int *i2)
{
return (*i2 < *i1) - (*i1 < *i2);
}
#define ROWS 5
#define COLS 5
/*
Assumes rows already sorted in descending order
NOTE: qsort calls the comparison function with pointers to elements
so this function has to be tweaked in case the matrix is an array of
pointers. In that case the function's declaration would be:
int rowcmp(int **pr1, int **pr2)
{
const int *r1 = *pr1;
const int *r2 = *pr2;
// the rest is the same
}
*/
int rowcmp(const int *r1, const int *r2)
{
int i = 0, cmp;
do {
cmp = intcmp(&r1[i], &r2[i]);
i++;
} while (i < COLS && cmp == 0);
return -cmp; /* return -cmp to sort in descending order */
}
int data[5][5] = {
{10,7,3,2,1},
{10,7,5,1,0},
{ 7,6,5,3,2},
{10,6,5,2,0},
{10,7,6,0,0}
};
void printmatrix()
{
int i, j;
for (i = 0; i < ROWS; i++) {
for (j = 0; j < COLS; j++) {
printf("%d ", data[i][j]); /* leaves a trailing space in each row */
}
printf("\n");
}
}
int main()
{
printmatrix();
qsort(data, 5, sizeof(data[0]), (int (*)(const void *, const void *))rowcmp);
printf("\n");
printmatrix();
return 0;
}
For the most flexible solution, I would define
struct row {
size_t len;
int *elems;
};
struct matrix {
struct row *rows;
size_t nrows;
};
and change the code accordingly.
NOTE: code not thoroughly tested, use with caution ;)
First of all, are you sure that the 1 on row 3,col 5 should be there and not on the last line?
Anyway, an efficient way to achieve what you want is:
compute the frequency array
declare a new matrix
go from the highest element (10 in your case) from frequency array and put in your matrix using your desired format.
It is time-efficient because you don't use any sorting algorithm, thus you don't waste time there.
It is NOT space-efficient because you use 2 matrices and 1 array, instead of only 1 matrix as suggested in other posts, but this should not be a problem, unless you use matrices of millions of rows and columns
C code for frequency array:
int freq[11] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
for(int i=0; i<NO_ROWS; i++) {
for(int j=0; j<NO_COLS; j++) {
if(MATRIX[i][j]!=null && MATRIX[i][j]>0 && MATRIX[i][j]<11) {
freq[MATRIX[i][j]]++;
}
}
}
C code for computing the new matrix dimensions
(assuming you want to keep the number of rows)
OUTPUT_MATRIX[100][100] /*I declared it statically, but I would advise to make it dinamically */
/* first, compute the number columns.
To do so, we need the number of elements
(we get them by simply summing up frequency array's elements) */
int s=0;
for(int i=0; i<11; i++) {
s+=frequency[i];
}
int addOne = 0 /* boolean value to check if we will have to add one extra column for safety */
if(s % NO_ROWS) {
addOne = 1; /* division is not even, so we will have to add extra column */
}
NO_COLS = s/NO_ROWS + addOne;
Now, final part, assigning the values from frequency array to the OUTPUT_MATRIX
int k=0;
int currentNumber = 10; /* assigning starts from 10 */
for(int i=0; i<NO_ROWS; i++) {
for(int j=0; j<NO_COLS; j++) {
if(currentNumber>0) {
if(frequency[currentNumber]==0 || k>=frequency[currentNumber]) {
currentNumber--;
k=0;
}
OUTPUT_MATRIX[i][j] = frequency[currentNumber];
k++;
} else {/*here, you can assign the rest of the value with whatever you want
I will just put 0's */
OUTPUTMATRIX[i][j] = 0;
}
}
}
Hope this helps!
This is what I do in C++ to reorder a matrix:
// b is the matrix and p is an array of integer containing the desired order of rows
for(i=0; i<n; i++){
if( p[i]==i )
continue;
b[i].swap(b[p[i]]);
j = p[i]; // New row i position
// Update row i position to new one
for(int k=i+1; k<n; k++){
if( p[k] == i )
p[k] = j;
}
printRow( b[i] );
}
You need to define an array of pointers of the data type you use and then you can reorder your matrix.
for example your matrix is: arr[5][10], and you want to print line 4 before line 3:
int *[5] arr2;
arr2[0] = &arr[0][0];
arr2[1] = &arr[1][0];
arr2[2] = &arr[2][0];
arr2[3] = &arr[4][0];
arr2[4] = &arr[3][0];
in regard to how will the ordering algorithm work, i would suggest placing a header in the start of each array in the matrix which will tell you how many elements it has(basically the first element of each array can be a counter of the total elements) afterwards you can order the strings by comparing the header, and if it is equal comparing the first element and so on. this can be done in a loop that iterates as many times as there are elements in the array, when the elements are not equal, break out of the loop.
hope this helps.
I'm trying to calculate the dispersion between two values, one I get from and certain parameter('age') from each entry on the array of structures.
I've got an auxiliary .txt file and, the whole point of this is to go through each of the lines of the .txt file individually (each line is a string). It's better if I state an example, so, here we go:
matrix[n][n]:
1 2 3 4
1 2 3
1 2
So, the structure would look a bit like this:
struct person {
int id; //where im comparing between the matrix and the structure;
int age; //what I need to calculate the dispersion
}
I gotta compare the each value of each line of the .txt, and if it matches any of the id's on the structure, I gotta get its age. Now comes the tricky part.
To calculate the dispersion I need to get the following working out for me:
Let's take as example the first row of the .txt file: the dispersion would be:
let's say that 'age' = age of the id (n);
//in this case nGroups = 6 (number of age(n)-age(m) operations)
dispersion(first_row)= [ [|age(1)-age(2)|] + [|age(1)-age(3)|] + [|age(1)-age(4)|] + [|age(2)-age(3)|] + [|age(2)-age(4)|] + [|age(3)-age(4)|] ]/nGroups
So I have to do this for each row of the matrix. I've tried it and managed the following code, but in the 'math' part my brain freezes a bit.
// going through each line of the matrix
for(i=0; i<nconjuntos; i++) {
// going through each column of the matrix
for(j=0; j<strlen(aux[i]); j++) {
// going through all the structures in the structure array
for(k=0; k<TOTAL; k++) {
// comparing each number with it's id equivalent in
// each structure.id parameter in the array
if(aux[i][j] - 48 == pessoas[k].id) {
}
}
}
}
Any help that would help me to advance in my code would be really appreciated!
You have two problems here requiring a solution:
Match the id in the matrix with the id in the structure and get a list of ages for a given row
Calculate the dispersion
It's probably easiest if you separate these two tasks instead of doing them both inside the same nested for loop. You can write a function to calculate the dispersion according to the formula you gave like this:
double calculateDispersion(double* values, int count)
{
if(count < 2)
return 0.0; // need at least 2 values
double total = 0.0;
// iterate through each combination of values and sum the absolute
// differences of each combination:
int i, j;
for(i = 0; i < (count - 1); i++)
{
for(j = i + 1; j < count; j++)
{
double difference = values[i] - values[j];
if(difference < 0.0) // find absolute value
difference = 0.0 - difference;
total += difference; // add to the total
}
}
int groups = (count * (count - 1)) / 2;
return total / (double)groups;
}
Inside your main loop create an array of doubles equal in size to the largest row in your matrix, to store the ages for the current row (or floats, but using ints will give you rounding errors). Fill it up by cross-referencing with the structs containing the id and age. Then call calculateDispersion() to calculate the dispersion for the row.
Something like roughly this:
double rowArray[MAX_SIZE]; // or initialize to maximum matrix row length dynamically
// going through each line of the matrix
for(i=0; i<nconjuntos; i++) {
int count = 0;
// going through each column of the matrix
for(j=0; j<strlen(aux[i]); j++) {
// going through all the structures in the structure array
for(k=0; k<TOTAL; k++) {
// comparing each number with it's id equivalent in
// each structure.id parameter in the array
if(aux[i][j] - 48 == pessoas[k].id) {
// set array value:
rowArray[count++] = (double)pessoas[k].age;
break; // break out of the loop
}
}
}
// compute the dispersion for the row:
doubleDispersion = calculateDispersion(rowArray, count);
}