Question

I have a function below and it is a recursive since it calls itself at the end, but how to I change it non-recursive?

int ACR(int q, int*a, int n, int i){
    if(i>=n){
        return 0;
    }
    else{
        if(a[i] == q){
            return 1;
        }
        else{
            return ACR(q,a,n,i+1);
        }
    }
}

Answer 1

You can use a loop instead

int ACR(int q, int*a, int n, int i){
    int j;
    for (j=i; j<n; j++) {
        if (a[j] == q) {
            return 1;
        }
    }
    return 0;
}

Each call to the iterative version of ACR tested whether a single element of the array a matched the value of q. If we reached the end of the array without a match, we returned 0. Its easy to translate this into a loop.

Note that i may no longer be required as an argument if you always want to search the full array (i.e. start at index 0).