C program doesn't print output terminal

Question

This is a program to store all possible combinations of given array in the array ans[][].

#include <stdio.h>

int ingredients = 10;
int ans[10][10];
int x = 0;

void makeCombination(int arr1[], int data[], int st, int end, int index, int r);

void CombinationDisplay(int arr1[], int n, int r) {
    int data[r];
    makeCombination(arr1, data, 0, n - 1, 0, r);
}

void makeCombination(int arr1[], int data[], int st, int end, int index, int r) {
    if (index == r) {
        for (int j = 0; j < r; j++)
            ans[x][j] = data[j];
        x++;
        return;
    }
    for (int i = st; i <= end && end - i + 1 >= r - index; i++) {
        data[index] = arr1[i];
        makeCombination(arr1, data, i + 1, end, index + 1, r);
    }
}

int main() {
    int arr1[ingredients], i;

    for (i = 0; i < ingredients; i++)
        arr1[i] = i;
    int n = sizeof(arr1) / sizeof(arr1[0]);

    for (int r = 0; r < ingredients; r++)
        CombinationDisplay(arr1, n, r);
    
    for (i = 0; i < ingredients; i++) {
        for (int j = 0; j < i; j++) {
            printf("%d", ans[i][j]);
        }
        printf("\n");
    }
    return 0;
}

It should store all the combinations in an array ans and print it. However, it does not show any errors, nor output in the terminal.

no. I get stuff like: 0 01 012 0123 01235 012456 0134567 02345678 123456789 — 4386427
– 4386427, Commented Feb 6, 2022 at 6:06
It can also be that the program has undefined behavior. What output would you expect for int ingredients = 2; ? — 4386427
– 4386427, Commented Feb 6, 2022 at 6:11

chqrlie · Accepted Answer · 2022-02-06 07:26:05Z

1

There are multiple problems in your code:

int ans[10][10]; is not large enough for all combinations of 10 elements: there are 2¹⁰ possible combinations (subsets of a set of 10 elements).
printing initial subsets of subsets would produce many duplicates.
a recursive approach is not as simple as an iterative approach for this problem.

Here is a modified version:

#include <stdio.h>

#define INGREDIENTS 10  // must be in the range 1 to 30 for 32-bit int

int main() {
    for (int i = 0; i < (1 << INGREDIENTS); i++) {
        for (int j = 0; j < INGREDIENTS; j++) {
            if (i & (1 << j))
                printf("%u ", j);
        }
        printf("\n");
    }
    return 0;
}

answered Feb 6, 2022 at 7:26

chqrlie

152k12 gold badges145 silver badges231 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

C program doesn't print output terminal

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related