Algorithm for truck moving around a circle of gas stations

Question

You have a truck moving around a circular track with gas stations spaced out around the circle. Each station has a finite amount of gas. The gas tank on the truck is infinit

Answer 1

static int find(int A[], int B[]) {     
    for (int start = 0; start < A.length; start++) {
        int x = findIndex(A, B, start);
        if (x != -1)
            return x;
    }
    return -1;
}

static int findIndex(int A[], int B[], int start) {
    int total=0;
    int N = A.length;
    for (int i = start; i < start + A.length; i++) {
        int c = A[i % N] - B[i % N];
        total += c;
        if (total < 0) {
            total = 0;
            return -1;
        }
    }
    return start;
}

Test cases:

1. Test case A : { 1, 2, 3, 4, 5 }, B : { 1, 3, 2, 4, 5 } --> index 2
2. Test case A : {2,2,1}, B : {2,1,2} index --> 0
3. Test case A : {1,2}, B {2,1} --> index 1
4. Test case A : {1,2,1}, B {2,1,3} --> index -1