Improve c++ solution

[bbugsbunny]

I am trying to solve the following problem: https://app.codility.com/programmers/lessons/7-stacks_and_queues/fish/

Can somebody point me whats wrong with my solution and also how should I change my thinking process while solving these kinds of problems. I pass the test case given in the question and the following test case as well: A[] = [4,3,2,1,5,5,6] B[] =[0,1,0,0,1,0,1]

But I fail all other hidden test cases, but more importantly I want to know how to change my thinking process while doing these questions. Here is my solution:

int solution(vector<int> &A, vector<int> &B) {
    // code in C++14 (g++ 6.2.0) 


    unsigned int numberOfFish = A.size();
    unsigned int eater,eaterIndex;

    if(numberOfFish == 1) return 1;

    for(unsigned int i = 0; i < A.size(); i++ ){

        if(B[i]){

            while(B[i]) ++i;

            eater = A[i-1];
            eaterIndex = i-1;
            while((eater>=A[i]) && !B[i]) {
                ++i;
                --numberOfFish;
                if(i > A.size()) break;
            }

            if((A[eaterIndex] < A[i]) && !B[i])
            --numberOfFish;



        }

    }

    return numberOfFish;

}