构建乘积数组

题目描述

给定一个数组A[0,1,...,n-1],请构建一个数组B[0,1,...,n-1],其中B中的元素B[i]=A[0]*A[1]*...*A[i-1]*A[i+1]*...*A[n-1]。不能使用除法。

 

class Solution {
public:
    vector<int> multiply(const vector<int>& A) {
        vector<int> result,result1,result2;
        if (A.size() == 0)
            return result;
        if(A.size() == 1)
        {
            result.push_back(0);
            return result;
        }
        result1.push_back(1);
        int len = A.size();
        for(int i = 1 ;i < len ;++i)
        {
            result1.push_back(result1[i-1]*A[i-1]);
        }
        for(int i = 0 ;i < len ;++i)
        {
            result2.push_back(1);
        }
        for(int i = len - 2 ;i >= 0 ; --i)
        {
            result2[i] = result2[i+1]*A[i+1];
        }
        for(int i = 0 ;i < len ;++i)
        {
            result.push_back(result1[i]*result2[i]);
        }
        return result;
    }
};