this program is "calculating" all subsets of the array source. I need to store the resulting values in another 2D filed named polje. If I just use the printf("%d %d %d ", source[i][0], source[i][1], source[i][2]); the code works fine but something fails when it is trying to copy everything into the resulting field. I suppose I am dogin something wrong in the indexing of the array polje.
#include <stdio.h>
#include <stdlib.h>
int main(int argc, char** argv) {
int f;
int i,j;
int source[2][3] = {{0,3,5},{3,4,2}};
int currentSubset = 3;
int polje[8][3];
for(i=0;i<8;i++){
for(j=0;j<3;j++){
polje[i][j]=0;
}}
int tmp;
while(currentSubset)
{
tmp = currentSubset;
for( i = 0; i<3; i++)
{
if (tmp & 1)
{
printf("%d %d %d ", source[i][0], source[i][1], source[i][2]); //writes out everything I want
polje[currentSubset][0]=source[i][0];
polje[currentSubset][1]=source[i][1];
polje[currentSubset][2]=source[i][2];
}
tmp >>= 1;
}
printf("\n");
currentSubset--;
}
for(i=0;i<8;i++){
for(j=0;j<3;j++){
printf("%d ", polje[i][j]);
}printf("\n");}
return (EXIT_SUCCESS);
}
The output field should be:
0 3 5
3 4 2
3 4 2
0 0 0
0 3 5
0 0 0
0 0 0
0 0 0
But instead it is:
0 3 5
3 4 2
3 4 2
0 0 0
*0 0 0*
0 0 0
0 0 0
0 0 0
tmp is a bit mask with only two bits, so the inner loop should be for ( i = 0; i < 2; i++ ).
Also the correct index into the polje array is polje[currentSubset * 2 + i][0] since each subset in polje takes two spaces and i is either 0 or 1.
I think you just have a logic error. Your loop's skeleton is:
currentSubset = 3;
while ( currentSubset )
{
// ...
polje[currentSubset][...] = ...;
// ...
currentSubset--;
}
So you never write to any rows except the first three.
Related
I have an array called int arr[10] = {1,2,3,4,5}
From my understanding the rest of the array is filled with 0's.
My questions is if its a fixed array length how can I put the first index behind the last index that is not a 0. For example
I believe the 0 is not shown in real printf but I am including it for illustration purposes
for (int i = 0 ; i < 10 ; i++)
{
print("%i" , arr[i]);
}
The output
1 2 3 4 5 0 0 0 0 0
If i move the first index to the back of the 5 like so
for (int i = -1 ; i < 10 ; i++)
{
arr[i] = arr[i + 1];
print("%i" , arr[i]);
}
Will the output put the 1 behind the 5 or at the back of the whole array?
2 3 4 5 1 0 0 0 0 0
or because there is 0s then
2 3 4 5 0 0 0 0 0 1
If my question is unclear please tell me and I will try explain it.
The output
1 2 3 4 5 0 0 0 0 0
No, the actual output is
1234500000
Your code has undefined behavior. The first iteration of the loop (with i = -1) tries to assign to arr[-1], which does not exist:
arr[i] = arr[i + 1];
Similarly, the last iteration (with i = 9) tries to read from arr[10], which also does not exist.
I'm not sure why you think your code will move the first element back.
From my understanding the rest of the array is filled with 0's
You are right.:)
If i move the first index to the back of the 5 like so
for (int i = -1 ; i < 10 ; i++)
{
arr[i] = arr[i + 1];
print("%i" , arr[i]);
}
then you will get undefined behavior because the indices -1 and 10 are not valid indices.
It seems what you are trying to do is the following
#include <stdio.h>
#include <string.h>
int main(void)
{
enum { N = 10 };
int a[N] = { 1, 2, 3, 4, 5 };
size_t pos = 0;
while ( pos < N && a[pos] != 0 ) ++pos;
if ( pos != N && !( pos < 3 ) )
{
int tmp = a[0];
pos -= 2;
memmove( a, a + 1, pos * sizeof( int ) );
a[pos] = tmp;
}
for ( size_t i = 0; i < N; i++ ) printf( "%d ", a[i] );
putchar( '\n' );
return 0;
}
The program output is
2 3 4 1 5 0 0 0 0 0
I have some dificulties in creating the following array. My task is to fill using recursion a 2D array with all the possible combinations of 0 and 1 taken m times in lexical order. Mathematically speaking there are 2 ^ m combinations.My program just fills the first 3 rows of the array with the same order 0 1 0 1 and then just prints for the rest of the rows 0 0 0 0.
Example
m=4
0 0 0 0
0 0 0 1
0 0 1 0
0 0 1 1
0 1 0 0
0 1 0 1
0 1 1 0
0 1 1 1
1 0 0 0
1 0 0 1
1 0 1 0
1 0 1 1
1 1 0 0
1 1 0 1
1 1 1 0
1 1 1 1
This is my code so far and I appreciate if someone could correct it and explain me what I am doing wrong as I can't spot the mistake myself
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <math.h>
void *safeMalloc(int n) {
void *p = malloc(n);
if (p == NULL) {
printf("Error: malloc(%d) failed. Out of memory?\n", n);
exit(EXIT_FAILURE);
}
return p;
}
void combine(int** arrTF,int m,int n,int row,int col){
if(m==0){
if(row<pow(2,m)){
row++;
combine(arrTF,n,n,row,0);
}else{
return;
}
}else{
arrTF[row][col]=0;
col++;
combine(arrTF,m-1,n,row,col);
arrTF[row][col]=1;
col++;
combine(arrTF,m-1,n,row,col);
}
}
int main(int argc, char *argv[]) {
int m
scanf("%d",&m);
int** arrTF;
arrTF = safeMalloc(pow(2,m)*sizeof(int *));
for (int r=0; r < pow(2,m); r++) {
arrTF[r] = safeMalloc(m*sizeof(int));
}
for(int i=0;i<pow(2,m);i++){
for(int j=0;j<m;j++){
arrTF[i][j]=0;
}
}
combine(arrTF,m,m,0,0);
for(int i=0;i<pow(2,m);i++){
for(int j=0;j<m;j++){
printf("%d ",arrTF[i][j]);
}
printf("\n");
}
return 0;
}
You want all the possible (2^m) combinations of 0's and 1's taken m times in lexical order and you are using a 2D array to store the result.
Things would be very easy if you just want to print all the possible combination of 0's and 1's instead of storing it in 2D array and printing array later.
Storing a combination of 0's and 1's to 2D array is a little bit tricky as every combination is one element of your 2D array.
You want to generate the combination of 0's and 1's in accordance with the recursive algorithm.
So, let's say, at some stage if your algorithm generates the combination 0010 which is stored in an element in 2D array.
And the next combination would be 0011 which the recursive algorithm will generate just by changing the last number from 0 to 1 in the last combination (0010).
So, that means everytime when a combination is generated, you need to copy that combination to its successive location in 2D array.
For e.g. if 0010 is stored at index 2 in 2D array before the algorithm starts computing the next combination, we need to do two things:
Copy the elements of index 2 to index 3
Increase the row number so that last combination will be intact
(Say, this is 2D array)
|0|0|0|0| index 0
|0|0|0|1| index 1
|0|0|1|0| index 2 ---> copy this to its successive location (i.e. at index 3)
|0|0|1|1| index 3 ---> Last combination (index 2) and the last digit is changed from 0 to 1
.....
.....
.....
This we need to do for after every combination generated.
Now, I hope you got where you are making the mistake.
Few practice good to follow:
If you want to allocate memory as well as initialized it with 0, use calloc instead of malloc.
Any math function you are calling again and again for the same input, it's better to call it once and store the result in a variable and use that result where ever required.
Do not include any header file which is not required in your program.
Once done, make sure to free the dynamically allocated memory in your program.
I have made the corrections in your program:
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
void *safeMalloc(size_t n, size_t size) {
void *p = calloc(n, size);
if (p == NULL) {
printf("Error: calloc(%zu) failed. Out of memory!\n", n);
exit(EXIT_FAILURE);
}
return p;
}
void deallocate(int ** ptr, int row) {
for(int i = 0; i<row; i++)
free(ptr[i]);
free(ptr);
}
void combine(int **arrTF, int m, int max_col, int max_row) {
static int row;
if(m==0){
int i;
if (row<(max_row - 1))
{
for(i=0; i<max_col; i++)
arrTF[row+1][i] = arrTF[row][i];
}
row++;
return;
} else {
arrTF[row][max_col-m] = 0;
combine(arrTF, m-1, max_col, max_row);
arrTF[row][max_col-m] = 1;
combine(arrTF, m-1, max_col, max_row);
}
}
int main(int argc, char *argv[]) {
int** arrTF;
int m, max_row;
printf ("Enter number: \n");
scanf("%d", &m);
max_row = pow(2, m);
arrTF = safeMalloc(max_row, sizeof(int *));
for (int r=0; r<max_row; r++) {
arrTF[r] = safeMalloc(m, sizeof(int));
}
combine(arrTF, m, m, max_row);
for(int i=0; i<max_row; i++) {
for(int j=0; j<m; j++) {
printf("%d ", arrTF[i][j]);
}
printf("\n");
}
deallocate(arrTF, max_row);
return 0;
}
Output:
$ ./a.out
Enter number:
2
0 0
0 1
1 0
1 1
$ ./a.out
4
0 0 0 0
0 0 0 1
0 0 1 0
0 0 1 1
0 1 0 0
0 1 0 1
0 1 1 0
0 1 1 1
1 0 0 0
1 0 0 1
1 0 1 0
1 0 1 1
1 1 0 0
1 1 0 1
1 1 1 0
1 1 1 1
Hope this helps.
I am trying to set all the values in my 2D array to 0 and then print all the scores back to make sure they are correct.
struct Game {
int GameScoresHome[10][10];
};
int main() {
struct Game game;
memset(game.GameScoresHome, 0, sizeof game.GameScoresHome);
for (int x=0;x<100;x++) {
int y = floor(x/10);
printf("%d ",game.GameScoresHome[x][y]);
}
return 0;
}
The current output is:
0 0 0 0 0 0 0 0 0 0 0 0 822083893 32767 32767 32767 32767 32767 32767 1651067951 1634028652 1345283180 1702057263 1701080931 2054842477 1866870631 1885417061 1647262318 1146113364 896624241 1280918623 1919052108 1819042146 1818850626 1634956149 1852133983 1264923239 792545364 1666723698 1836345960 1163089152 1949263220 1919250021 1868774725 1213481296 796026224 1785230711 1650803759 792546380 1213481296 1868781615 1752003690 6780258 1497628720 778396783 1920232291 792545364 1666723698 1836345960 1735746149 796026224 1785230711 1650803759 0 0 3 0 7 0 -2147482624 0 0 0 0 0 0 0 0 0 0 233472 1869045599 48 1868783455 5312 1633967967 3480 1818320735 304 1919115103 0 1852796269 0 115 0 72 0 1227 0 0
The first 11 zeros are as they should be then it all goes wrong. What's going on?
You're accessing memory outside the array.
Your x variable iterates from 0 to 99.
for (int x=0;x<100;x++)
But your array has only 10 rows.
int GameScoresHome[10][10];
One fix would be to use simple nested loops.
for (int x=0;x<10;x++) {
for (int y=0;y<10;y++) {
printf("%d ",game.GameScoresHome[x][y]);
}
}
Nested loops would also make it easy to include a newline after each row.
for (int x=0;x<10;x++) {
for (int y=0;y<10;y++) {
printf("%d ",game.GameScoresHome[x][y]);
}
printf("\n");
}
In your code
for (int x=0;x<100;x++) {
int y = floor(x/10);
printf("%d ",game.GameScoresHome[x][y]);
}
the x value is going out of bound. Maybe you want to take a %10 value of x and change the index locations, like
printf("%d ",game.GameScoresHome[y][x%10]);
or, use a nested loop to maintain two indexes separately.
What about?
struct Game game = {.GameScoresHome = {0}};
for (int x=0;x<10;x++) {
for (int y=0;y<10;y++) {
printf("%d ",game.GameScoresHome[x][y]);
}
printf("\n");
}
Write the loop simpler
for ( int x = 0; x < 100; x++) {
printf("%d ",game.GameScoresHome[x / 10][x % 10]);
}
or
for ( int x = 0; x < 100; x++) {
printf("%d ",game.GameScoresHome[x / 10][x % 10]);
if ( x % 10 == 9 ) printf( "\n" );
}
As for your loop then x is being changed from 0 up to 100 and as result using x as the first index in the statement
printf("%d ",game.GameScoresHome[x][y]);
^^^
is invalid. And y is calculated incorrectly.
I'm trying to read a text file containing integers via stdin and store the values in a 9x9 array (please note that the file must be read via stdin and not as an arg)
This is what I have:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
int main()
{
int puzzle[9][9];
int i,j,count=0;
char value[81];
for( i = 0; i < 9; i++ ) {
for( j = 0; j < 9; j++ ) {
scanf("%c", &value[count]);
puzzle[i][j] = value[count] - '0';
count++;
}
}
}
But it doesn't seem to convert the ASCII characters from scanf to int, which is what I thought the value[count] - '0' was supposed to do, so I end up getting values like this:
-16-16-160-16-160-16-161
Basically i'm trying to do exactly whats described in this thread, but in C instead of C++:
How to convert a 2d char array to a 2d int array?
Edit -
The input file looks like this (contains both white space and new lines):
0 0 1 9 0 0 0 0 8
6 0 0 0 8 5 0 3 0
0 0 7 0 6 0 1 0 0
0 3 4 0 9 0 0 0 0
0 0 0 5 0 4 0 0 0
0 0 0 0 1 0 4 2 0
0 0 5 0 7 0 9 0 0
0 1 0 8 6 0 0 0 7
7 0 0 0 0 9 2 0 0
The problem is not with the conversion line puzzle[i][j] = value[count] - '0';. The problem lies with the following scanf() statement, scanf("%c", &value[count]);. The scanf is reading the first white space. Use scanf(" %c", &value[count]); to read the input.
%c does eactly what it should: it reads one character. D'oh, it's whitespace? That doesn't matter. This is why...
... you shouldn't use %c but %d for scanning integers;
...you shouldn't use scanf() at all for something simple like this.
What I'd do if I were you:
int matrix[9][9];
int i = 0;
char buf[0x100];
while (fgets(buf, sizeof(buf), stdin)) {
char *end;
char *p = strtok_r(buf, " ", &end);
while (p) {
matrix[i / 9][i % 9] = strtol(p, NULL, 10);
i++;
p = strtok_r(NULL, " ", &end);
}
}
Is there any reason this doesn't work? Scan them in as integers.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
int main()
{
int puzzle[9][9];
int i,j,count=0;
char value[81];
for( i = 0; i < 9; i++ ) {
for( j = 0; j < 9; j++ ) {
scanf("%d", &value[count]);
puzzle[i][j] = value[count];
printf("%d", puzzle[i][j]); //to verify it is stored correctly
count++;
}
}
}
EDIT: since you said it's coming from a file, i copy/pasted the sample file you gave into C:\file.txt, and the following code appears to work just dandy.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
int main()
{
FILE *fp;
int puzzle[9][9];
int i,j,count=0;
int value[81];
fp = fopen("C:\\file.txt", "r");
for( i = 0; i < 9; i++ ) {
for( j = 0; j < 9; j++ ) {
fscanf(fp, " %d", &value[count]);
puzzle[i][j] = value[count];
printf("element %d is %d\n",count, puzzle[i][j]);
count++;
}
}
}
I want to generate permutations of string of 5 0s followed by the permutations of 4 0s and a single 1, followed by the permutations of 3 0s with 2 1s etc? My code is as follows:
#include<stdio.h>
int main(){
int i,j,k,l,s[5];
for(i=0;i<5;i++)
s[i]=0;
for(k=0;k<5;k++)
printf("%d ",s[k]);
printf("\n");
printf("---------------------------------------------\n");
for(i=0;i<5;i++){
for(j=0;j<5;j++)
if(i==j)
s[j]=1;
else
s[j]=0;
for(k=0;k<5;k++)
printf("%d ",s[k]);
printf("\n");
}
printf("---------------------------------------------\n");
for(i=0;i<5;i++){
for(k=0;k<5;k++)
s[k]=0;
s[i]=1;
for(j=i+1;j<5;j++){
s[j]=1;
for(k=0;k<5;k++)
printf("%d ",s[k]);
printf("\n");
for(k=j;k<5;k++)
s[k]=0;
}
}
printf("---------------------------------------------\n");
for(i=0;i<5;i++){
for(j=i+1;j<5;j++){
for(k=0;k<5;k++)
s[k]=0;
s[i]=1;
s[j]=1;
for(l=j+1;l<5;l++){
s[l]=1;
for(k=0;k<5;k++)
printf("%d ",s[k]);
printf("\n");
for(k=l;k<5;k++)
s[k]=0;
}
}
}
}
So output is
0 0 0 0 0
---------------------------------------------
1 0 0 0 0
0 1 0 0 0
0 0 1 0 0
0 0 0 1 0
0 0 0 0 1
---------------------------------------------
1 1 0 0 0
1 0 1 0 0
1 0 0 1 0
1 0 0 0 1
0 1 1 0 0
0 1 0 1 0
0 1 0 0 1
0 0 1 1 0
0 0 1 0 1
0 0 0 1 1
---------------------------------------------
1 1 1 0 0
1 1 0 1 0
1 1 0 0 1
1 0 1 1 0
1 0 1 0 1
1 0 0 1 1
0 1 1 1 0
0 1 1 0 1
0 1 0 1 1
0 0 1 1 1
Output is ok. However in my code I use
different for loops for different cases.
Is it possible to use better approach so
that length of the code is reduced?
One approach follows. This solution needs O(n) space and each output string requires O(n) time.
#include <stdio.h>
#include <stdlib.h>
char *buf;
// Print combinations of m 1's in a field of n 0/1's starting at s.
void print_combinations(char *s, int n, int m)
{
// If there is nothing left to append, we are done. Print the buffer.
if (m == 0 && n == 0) {
*s = '\0';
printf("%s\n", buf);
return;
}
// Cut if there are more 1's than positions left or negative numbers.
if (m > n || m < 0 || n < 0) return;
// Append a 0 and recur to print the rest.
*s = '0';
print_combinations(s + 1, n - 1, m);
// Now do the same with 1.
*s = '1';
print_combinations(s + 1, n - 1, m - 1);
}
int main(void)
{
int n = 5;
buf = malloc(n + 1);
for (int m = 0; m <= n; m++) {
print_combinations(buf, n, m);
printf("-----\n");
}
return 0;
}
You could use a recursive function like so - you don't have to print the result when finished, you could add it to a list etc.
The function works by starting with an empty string. At each step you add one more character - in this case you add either a 0 or a 1.
If a 1 is added we account for this by decrementing the ones value on the next call to the function. (In a more general case you could pass a list of all the elements to be permuted - then the process would be to pick from this list, add it to your permutation and remove it from the list. You repeat that until the list is empty and you have permuted all of the elements in the list.)
When the string reaches the desired length we have finished and so we return.
#include <stdio.h>
void recurse(char *str, int length, int maxLength, int ones)
{
if (length == maxLength)
{
// we are finished
printf("%s\n", str);
return;
}
if (ones > 0)
{
// put a 1 into the new string
str[length] = '1';
recurse(str, length + 1, maxLength, ones - 1);
}
if (ones < maxLength - length)
{
// there are still spaces for 0s
// put a 0 into the string
str[length] = '0';
recurse(str, length + 1, maxLength, ones);
}
}
int main()
{
const int maxLength = 5;
char buffer[maxLength + 1];
buffer[maxLength] = 0;
int ones;
for (ones = 0; ones <= maxLength; ones++)
{
printf("Ones: %i\n", ones);
recurse(buffer, 0, maxLength, ones);
printf("\n");
}
return 0;
}
The output looks like this:
Ones: 0
00000
Ones: 1
10000
01000
00100
00010
00001
Ones: 2
11000
10100
10010
10001
01100
01010
01001
00110
00101
00011
Ones: 3
11100
11010
11001
10110
10101
10011
01110
01101
01011
00111
Ones: 4
11110
11101
11011
10111
01111
Ones: 5
11111
Finally, unless you really want to/need to learn/use C, I would recommend using C++ because you get really nice features like std::vector and std::set and so many other things which will make your life so much easier. I would have written this completely different in C++.