C Exercises: Sum of the digits equals to another given number

Last update on September 19 2025 12:44:54 (UTC/GMT +8 hours)

Count digit combinations that sum to sss

Write a C program that reads n digits (given) chosen from 0 to 9 and prints the number of combinations where the sum of the digits equals another given number (s). Do not use the same digits in a combination.

For example, the combinations where n = 3 and s = 6 are as follows:
1 + 2 + 3 = 6
0 + 1 + 5 = 6
0 + 2 + 4 = 6

Sample Solution:

C Code:

#include<stdio.h>

// Recursive function to find combinations
int combination(int n, int s, int a) {
    int i, result = 0;

    // Base case: if n is 1, check if s is within valid range
    if (n == 1) {
        if (s >= a && s <= 9) {
            return 1;
        } else {
            return 0;
        }
    }

    // Iterate through possible values (a to 9)
    for (i = a; i <= 9; i++) {
        // Recursively call combination for (n-1) and adjust s and a values
        result += combination(n - 1, s - i, i + 1);
    }

    return result; // Return the total combinations
}

int main() {
    int n, s;

    printf("Input the number:\n");
    scanf("%d", &n);
    printf("\nSum of the digits:\n");
    scanf("%d", &s);

    if (n != 0 && s != 0) {
        printf("Number of combinations: %d\n", combination(n, s, 0));
    }

    return 0;
}

Sample Output:

Input the number:
3

Sum of the digits:
6
Number of combinations: 3

Flowchart:

C Programming Flowchart: Sum of the digits equals to another given number.

For more Practice: Solve these Related Problems:

Write a C program to generate all combinations of n digits (without repetition) whose sum equals s.
Write a C program to use nested loops to count unique digit combinations that add up to a specified sum.
Write a C program to implement a recursive backtracking algorithm to find digit combinations summing to s.
Write a C program to use dynamic programming to count the number of combinations where chosen digits sum to s.

Go to:

PREV : Find the most frequently occurring number in a sequence.
NEXT : Check if parallelogram is a rectangle or rhombus.

C programming Code Editor:

Have another way to solve this solution? Contribute your code (and comments) through Disqus.