Count the number of passing cars on the road.
Solution
int solution(vector<int> &A) { // write your code in C++11 (g++ 4.8.2) vector<int> pre_sum(A.size(), 0); int s = 0; for (size_t i = 0; i < A.size(); i++) { s += A[i]; pre_sum[i] = s; } int res = 0; for (int i = int(A.size() - 1); i >= 0; i--) { if (A[i] == 0) { res += (pre_sum[A.size() - 1] - pre_sum[i]); if (res > 1000000000) return -1; } } return res;}