238. [LeetCode] Product of Array Except Self

Given an array nums of n integers where n > 1, return an array output such that output[i] is equal to the product of all the elements of nums except nums[i].

Example:

Input:  [1,2,3,4]

Output: [24,12,8,6]

Note: Please solve it without division and in O(n).

Follow up:
Could you solve it with constant space complexity? (The output array does not count as extra space for the purpose of space complexity analysis.)

注释：用两个指针，前面的指针fromBegin比返回的res少乘一个当前的i，后面的指针也是如此。当i到达结尾时，前后都覆盖到了。

#include <cstdio>

#include <vector>

#include<iostream>

using namespace std;

class Solution {

public:

    vector<int> productExceptSelf(vector<int>& nums) {

        int n=nums.size();

        int fromBegin=;

        int fromLast=;

        vector<int> res(n,);

        for(int i=;i<n;i++){

            res[i]*=fromBegin;

            fromBegin*=nums[i];

            res[n--i]*=fromLast;

            fromLast*=nums[n--i];

        }

        return res;

    }

};

int main(){

    vector<int> temp;

    temp.push_back();

    temp.push_back();

    temp.push_back();

    temp.push_back();

    temp.push_back();

    temp.push_back();

    temp.push_back();

    temp.push_back();

    Solution test;

    test.productExceptSelf(temp);

    return ;

}

巴特西

238. [LeetCode] Product of Array Except Self

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