TheAlgorithms-C/misc/demonetization.c

// Recursion problem
//Given the denominations of currencies available in a system, find the number of ways an ATM machine can
//generate notes for an entered amount N.

#include <stdio.h>

int ways(int n, int a[], int k)
{
    if(n<0 || k<0) return 0;
    if(n == 0) return 1;
    if(k == 0) return 0;
    return ways(n, a, k-1) + ways(n-a[k-1], a, k);
}

int main()
{
    int m;
    int t;
    int n;

    printf("Number of coins? ");
    scanf("%d", &m);
    int coin[m], i;
    for(i=0; i<m; i++)
    {
        printf("coin? ");
        scanf("%d", &coin[i]);
    }

    printf("---- your requests --- \n");
    while(1)
    {
        printf("amount? exit(0) ");
        scanf("%d", &n);
        if (!n)
        {
            break;
        }
        printf("%d\n", ways(n, coin, m));
    }
    return 0;
}