题目描述

blablabla

样例

class Solution {
public:
    vector<int> multiply(const vector<int>& A) {
        //正着走一趟，反着走一趟
        //  1, A[0], A[0]*A[1], A[0]*A[1]*A[2],...A[0]*A[1] *...A[n - 1];
        // B[n - 1] * 1, B[n - 2] * A[n - 1] * A[n-2],...,B[0] * A[n - 1]*...A[1];
        if(A.empty()) return vector<int> ();
        int n = A.size();
        vector<int> B(n);
        for (int i = 0, tmp = 1; i < n; i ++) {
            B[i] = tmp;
            tmp = tmp * A[i];
        }
        for (int i = n - 1, tmp = 1; i >=0; i --) {
            B[i] *= tmp;
            tmp = tmp * A[i];
        }
        return B;
    }
};