How do this in C? Fill the matrix with random numbers.
Mapping the upper half of the matrix to the lower half
mirror symmetrically along the horizontal axis.
I made a function to output a multidimensional array and generate a random number. I am stuck on the next step: I don't know how to map the top half of the matrix to the bottom half mirror symmetrically along the horizontal axis.
const int m = 3, n = 4;
void InputMatrix(int x[m][n])
{
int i, j;
for (i = 0; i < m; i++)
for (j = 0; j < n; j++)
{
printf("Enter [%d][%d]:", i, j);
scanf("%d", &x[i][j]);
}
}
void PrintMatrix(int x[m][n])
{
int i, j;
printf("\n");
for (i = 0; i < m; i++)
{
for (j = 0; j < n; j++)
printf("%d\t", x[i][j]);
printf("\n");
}
}
void FillMatrix(int x[m][n])
{
int i, j;
for (i = 0; i < m; i++)
for (j = 0; j < n; j++)
{
x[i][j] = rand() % 100 - 50;
}
}
Related
Im trying to sort a matrix by the sum of its row's digits, from highest to lowest. I dont know if i explained that correctly so here's some photos explaining it.
This is what my code outputs. Basically, it asks you for m and n, which are the dimensions of the matrix. In this example it's a 3x4, 3 rows and 4 columns. Then, the matrix should be sorted by rows, by the sum of row's digits. Which means, instead of what's being outputted in the picture above, the correct result should be this:
I have no idea how to sort this from highest to lowest, i have been trying for hours to no avail.
Here's my code:
#include <stdio.h>
#define N 30
void main(){
double a[N][N], s[N], p;
int i, j, m, n, max;
while(1){
printf("\nm, n? ");
scanf("%d%d", &m, &n);
if(m <= 0 || m > N || n <=0 || n > N)
break;
for(i = 0; i < m; i++){
printf("%2d. row? ", i+1);
for(j = 0; j < n; scanf("%lf", &a[i][j++]));
}
for(i = 0; i < m; i++)
for(s[i] = j = 0; j < n; s[i] += a[i][j++]);
for(j = 0; j < n - 1; j++){
for(max = i, j = i+1; j < n; j++)
if(s[j] > s[max])
max = i;
if(max != j){
p = s[j];
s[j] = s[max];
s[max] = p;
for(j = 0; j < m; j++){
p = a[j][i];
a[j][i] = a[j][max];
a[j][max] = p;
}
}
}
printf("New matrix: \n");
for(i = 0; i < m; i++){
for(j = 0; j < n; printf("%8.2lf", a[i][j++]));
printf("\n");
}
for(j = 0; j < m; j++)
printf("-------------");
printf("\n");
for(j = 0; j < m; printf("%8.2f \n", s[j++]));
printf("\n");
}
}
You can sort the rows of the matrix from highest to lowest, using a simple bubble sort algorithm.Your code modified below:
int main() {
double a[N][N], s[N], p;
int i, j, m, n, max;
while (1) {
printf("\nm, n? ");
scanf("%d%d", & m, & n);
if (m <= 0 || m > N || n <= 0 || n > N)
break;
for (i = 0; i < m; i++) {
printf("%2d. row? ", i + 1);
for (j = 0; j < n; scanf("%lf", & a[i][j++]));
}
for (i = 0; i < m; i++)
for (s[i] = j = 0; j < n; s[i] += a[i][j++]);
for (i = 0; i < m - 1; i++) { // modified here
for (j = i + 1; j < m; j++) { // modified here
if (s[j] > s[i]) { // modified here
p = s[i];
s[i] = s[j];
s[j] = p;
for (int k = 0; k < n; k++) {
p = a[i][k];
a[i][k] = a[j][k];
a[j][k] = p;
}
}
}
}
printf("New matrix: \n");
for (i = 0; i < m; i++) {
for (j = 0; j < n; printf("%8.2lf", a[i][j++]));
printf("\n");
}
for (j = 0; j < m; j++)
printf("-------------");
printf("\n");
for (j = 0; j < m; printf("%8.2f \n", s[j++]));
printf("\n");
}
return 0;
}
Here's how i modified your code to achieve that:
Initialize a loop variable i to 0.
In the outer loop, run the inner loop j from i+1 to m-1.
In the inner loop, compare the sum of the row i with the sum of row
j. If the sum of row j is greater than the sum of row i, swap the
rows using a temporary variable.
After the inner loop finishes, increment the value of i by 1. Repeat
the outer loop until i becomes equal to m-1.
Output:
You can just use qsort to let it handle the sorting and item swapping. Then you only need to write the code for comparing two rows with each other.
Given something like this:
int matrix[3][4] =
{
{1,2,3,4},
{5,6,7,8},
{9,1,2,3},
};
You'd call qsort as:
qsort(matrix, 3, sizeof(int[4]), compare);
The only complexity is implementing the comparison callback function. There's two things to consider there:
We've told qsort that we have an array of 3 items, each of type int[4]. So the void pointers it passes along to us will actually be pointers to type int[4]. That is: int(*)[4].
qsort sorts in ascending order by default, where the item considered "less" ends up first. So we need to tweak that to get the largest item first.
Example:
int compare (const void* obj1, const void* obj2)
{
const int (*ptr1)[4] = obj1;
const int (*ptr2)[4] = obj2;
size_t sum1=0;
size_t sum2=0;
for(size_t i=0; i<4; i++)
{
sum1 += (*ptr1)[i];
sum2 += (*ptr2)[i];
}
if(sum1 > sum2) // largest sum considered "less" for qsort
return -1;
else
return 1;
return 0;
}
sum1 < sum2 would have placed the smallest row first.
Full example:
#include <stdio.h>
#include <stdlib.h>
int compare (const void* obj1, const void* obj2)
{
const int (*ptr1)[4] = obj1;
const int (*ptr2)[4] = obj2;
size_t sum1=0;
size_t sum2=0;
for(size_t i=0; i<4; i++)
{
sum1 += (*ptr1)[i];
sum2 += (*ptr2)[i];
}
if(sum1 > sum2) // largest sum considered "less" for qsort
return -1;
else
return 1;
return 0;
}
void print_matrix(size_t col, size_t row, int matrix[col][row])
{
for(size_t i=0; i<col; i++)
{
for(size_t j=0; j<row; j++)
{
printf("%d,", matrix[i][j]);
}
puts("");
}
}
int main (void)
{
int matrix[3][4] =
{
{1,2,3,4},
{5,6,7,8},
{9,1,2,3},
};
print_matrix(3,4,matrix);
puts("");
qsort(matrix, 3, sizeof(int[4]), compare);
print_matrix(3,4,matrix);
}
Write a program which will accept 2-dimensional square matrix and find out the transpose of it.
Program should not make use of another matrix
Hi I am trying to transpose a 2*2 matrix without using another matrix.
Is there anything wrong with my transpose logic?
I am a newbie
#include <stdio.h>
int main()
{
int mat[2][2];
int i, j, temp;
for (i = 0; i < 2; i++) {
printf("\nEnter elements of %d row of first matrix: ", i + 1); //i+1 so that it can print 1 row, 2 row, 3 row etc
for (j = 0; j < 2; j++) { //loop inside to loop to get value for a[0][0],a[0][1],a[0][2]
scanf("%d", &mat[i][j]);
}
}
printf("The matrix\n");
for (i = 0; i < 2; i++) {
for (j = 0; j < 2; j++) {
printf("%d\t", mat[i][j]);
}
printf("\n");
}
//transpose logic using same matrix
for (i = 0; i < 2; i++) {
for (j = 0; j < 2; j++) {
temp = mat[i][j];
mat[i][j] = mat[j][i];
mat[j][i] = temp;
}
}
printf("The transpose of the matrix is\n");
for (i = 0; i < 2; i++) {
for (j = 0; j < 2; j++) {
printf("%d\t", mat[i][j]);
}
printf("\n");
}
}
EDIT: I found an easier way to do it however I still don't understand why my transpose logic by using this
temp = mat[i][j];
mat[i][j] = mat[j][i];
mat[j][i] = temp;
cannot get it to transpose.
Below is my corrected answer
#include <stdio.h>
int main()
{
int mat[2][2];
int i, j, temp;
for (i = 0; i < 2; i++) {
printf("\nEnter elements of %d row of first matrix: ", i + 1);//i+1 so that it can print 1 row, 2 row, 3 row etc
for (j = 0; j < 2; j++) {//loop inside to loop to get value for a[0][0],a[0][1],a[0][2]
scanf("%d", &mat[i][j]);
}
}
printf("The matrix\n");
for (i = 0; i < 2; i++) {
for (j = 0; j < 2; j++) {
printf("%d\t", mat[i][j]);
}
printf("\n");
}
printf("The transpose of the matrix is\n");
for (i = 0; i < 2; i++) {
for (j = 0; j < 2; j++) {
printf("%d\t", mat[j][i]);
}
printf("\n");
}
}
Your program is a good attempt, but transposing the matrix is like reversing an array: you must stop half way to avoid swapping the transposed values twice, leading to the original matrix as you observe.
You should stop the inner loop when j == i, hence change the inner loop to:
for (j = 0; j < i; j++) { // j < i instead of j < 2
Here is a modified version:
#include <stdio.h>
int main() {
int mat[2][2];
int i, j, temp;
for (i = 0; i < 2; i++) {
printf("\nEnter elements of %d row of first matrix: ", i + 1);
for (j = 0; j < 2; j++) {
if (scanf("%d", &mat[i][j]) != 1)
return 1;
}
}
printf("The matrix:\n");
for (i = 0; i < 2; i++) {
for (j = 0; j < 2; j++) {
printf("%d\t", mat[i][j]);
}
printf("\n");
}
//transpose logic using same matrix
for (i = 0; i < 2; i++) {
for (j = 0; j < i; j++) {
temp = mat[i][j];
mat[i][j] = mat[j][i];
mat[j][i] = temp;
}
}
printf("The transpose of the matrix is:\n");
for (i = 0; i < 2; i++) {
for (j = 0; j < 2; j++) {
printf("%d\t", mat[i][j]);
}
printf("\n");
}
return 0;
}
Your corrected answer does not transpose the matrix at all, it merely outputs the transposed matrix. The matrix mat in memory is unchanged.
I've been trying to sort columns in a matrix (the dimensions are m,n <= 10) via the lexicographical order (if the columns share the same element, then we compare the elements in the row beneath etc.) with some additional conditions. I need to use functions to print the matrix, input random integers up to 5 as its elements and finally arrange the matrix. I think I got the printing and random inputs correctly but I can't figure out the sorting. Plus I can't use global variables which I have no idea how to do, since I haven't been shown. An example matrix would be :
#include <stdio.h>
#include <stdlib.h>
int main()
{
int m, n;
int mat[10][10];
void print_matrix()
{
int i, j;
for (i = 0; i < m; i++)
{
for (j = 0; j < n; j++)
{
printf("%d ", mat[i][j]);
}
printf("\n");
}
}
void random_int()
{
int i, j;
srand((unsigned)time(NULL));
for (i = 0; i < m; i++)
{
for (j = 0; j < n; j++)
{
mat[i][j] = rand() % 5;
}
}
}
void arrange()
{
int i, j, k, a;
for (j = 0; j < n; ++j)
{
for (i = 0; i < m; ++i)
{
for (k = i + 1; k < m; ++k)
{
if (mat[i][j] < mat[k][j])
{
a = mat[i][j];
mat[i][j] = mat[k][j];
mat[k][j] = a;
}
}
}
}
}
printf("Input the number of rows : ");
scanf("%d", &m);
printf("Input the number of columns: ");
scanf("%d", &n);
random_int(mat[m][n]);
print_matrix(mat[m][n]);
arrange(mat[m][n]);
print_matrix(mat[m][n]);
return 0;
}
Try this solution(will work for input 0-8 only), also used global variables:
There have multiple solutions. but is the easiest one.
I have converted each of the columns as an integer value. then bubble sorted the integers. After sorting. I have then converted the integer value to digits. (You have to know how to convert individual digits to multiple digit integer and multiple digit integers to single-digit.
Note I have added one(1) with each digit. Because the input can be zero(0). if you convert 0 0 2 1 to an integer will be only 21. the first two digits lost. So I have added 1. so 0 0 2 1 will be converted to 1132. I have done (added 1) for each input(deducted 1 after sorting). so it will not affect other inputs. Be careful input have to be from(0 to 8)
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
int m, n;
int mat[10][10];
int generatedNumber[10];
void print_matrix()
{
printf("The matrix is:\n");
int i, j;
for (i = 0; i < m; i++)
{
for (j = 0; j < n; j++)
{
printf("%d ", mat[i][j]);
}
printf("\n");
}
}
void random_int()
{
int i, j;
srand((unsigned)time(NULL));
for (i = 0; i < m; i++)
{
for (j = 0; j < n; j++)
{
mat[i][j] = rand() % 5;
}
}
}
void arrange()
{
int i, j, k, a;
for (j = 0; j < n; ++j)
{
int number = 0;
for (i = 0; i < m; ++i)
{
number = number * 10 + mat[i][j] + 1;///Adding one for avoiding zero(0)
}
generatedNumber[j] = number;
}
for(i = 0; i < n; i++)
{
for(j = 0; j < n-i-1; j++)
{
if( generatedNumber[j] > generatedNumber[j+1])
{
// swap the elements
int temp = generatedNumber[j];
generatedNumber[j] = generatedNumber[j+1];
generatedNumber[j+1] = temp;
}
}
}
for(i = 0; i < n; i++)///columwise
{
int generatedColumnvalue = generatedNumber[i];
for(j = m -1; j>= 0; j--)///row wise and fro last vaue to first
{
mat[j][i] = (generatedColumnvalue%10)-1;///removing extra added 1
generatedColumnvalue/=10;
}
}
}
int main()
{
printf("Input the number of rows : ");
scanf("%d", &m);
printf("Input the number of columns: ");
scanf("%d", &n);
random_int();
print_matrix();
arrange();
print_matrix();
return 0;
}
I have a 2d array filled with 0's and i'm trying to fill the main diagonal with numbers from 1 to n, this is the main code:
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
int main()
{
srand(time(NULL));
int m, n, i, j;
printf("Number of rows and columns:");
scanf("%d", &n);
int a[n][n];
for (i = 0; i < n; i++)
for(j = 0; j < n; j++)
a[i][j] = rand() % 1;
printf("The matrix is:\n");
for (i = 0; i < n; i++)
{
printf(" \n ");
for(j = 0; j < n; j++)
{
printf(" %d\t ", a[i][j]);
}
}
}
What I've tried to do is to fill the diagonal manually, but that's not what I want to do. I want to make it fill itself automatically. I need to do it without using any functions.
for (int i = 0; i < n; i++)
{
for (int j = 0; j < n; j++)
{
arr[i][j] = ((i == j) * (i + 1));
}
}
The simplest way is to add this part after you fill the matrix with zeros.
for (i = 0; i < n; i++)
arr[i][i] = i + 1;
The aim of the matrixMultiplier function is to multiply A * B, and then show the resulting matrix C, for any two square matrices A and B. A and B sizes are limited by 10*10.
When the user is asked the size of the matrix they wish to introduce, although A and B are 10*10, the function only works with the submatrices in A and B up to the dimension which the user has specified, say 3*3.
I've tested this out multiplying the 3*3 identity matrix by itself and it's not giving me the correct answer.
#include <stdio.h>
void matrixMultiplier(int A[][10], int B[][10], int C[][10], int n) {
int i, j, k;
for (i = 0; i < n; i++) {
for (k = 0; k < n; k++) {
C[i][k] = 0; /* Initialize output matrix to zero */
}
}
for (i = 0; i < n; i++) {
for (k = 0; k < n; k++) {
for (j = 0; j < n; j++) {
C[i][k] += A[i][j] * B[j][k];
}
}
}
printf("\n");
for (i = 0; i < n; i++) {
for (k = 0; k < n; k++) {
printf("%4d", C[i][k]);
}
printf("\n");
}
}
int main(void) {
int A[][10] = {{0}};
int B[][10] = {{0}};
int C[][10] = {{0}}; /* Initialize output matrix to zero */
int i, j;
int n;
printf("Enter square matrix dimension: ");
scanf("%d", &n);
for (i = 0; i < n; i++) {
for (j = 0; j < n; j++) {
printf("Assign a value: ");
scanf("%d", &A[i][j]);
}
printf("New row.\n");
}
for (i = 0; i < n; i++) {
for (j = 0; j < n; j++) {
printf("%4d", A[i][j]);
}
printf("\n");
}
for (i = 0; i < n; i++) {
for (j = 0; j < n; j++) {
printf("Assign a value: ");
scanf("%d", &B[i][j]);
}
printf("New row.\n");
}
for (i = 0; i < n; i++) {
for (j = 0; j < n; j++) {
printf("%4d", B[i][j]);
}
printf("\n");
}
matrixMultiplier(A, B, C, n);
return 0;
}
You need to use statically allocated arrays like this:
int A[10][10] = {{0}};
int B[10][10] = {{0}};
int C[10][10] = {{0}}; /* Initialize output matrix to zero */
As other commentators noticed, in C int A[][10] = {{0}}; is basically an equivalent of int A[1][10] = {{0}};, so only first rows are correctly set.
Take a look at this code:
#include <stdio.h>
#define MAX_SIZE 10
void matrixMultiplier(int A[][MAX_SIZE], int B[][MAX_SIZE], int C[][MAX_SIZE], int n)
{
int i, j, k;
for (i = 0; i < n; i++)
for (k = 0; k < n; k++)
for (j = 0; j < n; j++)
C[i][k] += A[i][j] * B[j][k];
printf("\nProduct Matrix C:\n\n");
for(i = 0; i < n; ++i)
{
for(j = 0; j < n; ++j)
printf("%4d", C[i][j]);
putchar('\n');
}
}
int main(void)
{
//int A[][10] = {{0}}; By initializing like this you are creating this int A[1][10] = {{0}};
int A[MAX_SIZE][MAX_SIZE] = {0};
int B[MAX_SIZE][MAX_SIZE] = {0};
int C[MAX_SIZE][MAX_SIZE] = {0};
int i, j, n;
printf("Enter square matrix dimension: ");
scanf("%d", &n);
printf("Input %d values row-wise, for matrix A: ", n*n);
for(i = 0; i < n; ++i)
for(j = 0; j < n; ++j)
scanf("%d", &A[i][j]);
printf("Input %d values row-wise, for matrix B: ", n*n);
for(i = 0; i < n; ++i)
for(j = 0; j < n; ++j)
scanf("%d", &B[i][j]);
printf("\nGiven Matrix A:\n\n");
for(i = 0; i < n; ++i)
{
for(j = 0; j < n; ++j)
printf("%4d", A[i][j]);
putchar('\n');
}
printf("\nGiven Matrix B:\n\n");
for(i = 0; i < n; ++i)
{
for(j = 0; j < n; ++j)
printf("%4d", A[i][j]);
putchar('\n');
}
matrixMultiplier(A, B, C, n);
return 0;
}
If you need more explanation about 2D arrays refer to this link