Maximum Product Subarray —— Leetcode

Find the contiguous subarray within an array (containing at least one number) which has the largest product.

For example, given the array [2,3,-2,4],

the contiguous subarray [2,3] has the largest product = 6.

class Solution {
public:
    /**
     * 为直观起见，函数用了空间复杂度为O(n)的vector
     * */
    int maxProduct(vector<int>& nums) {
        //这两个vector可用O(1)空间复杂度的常量值代替
        vector<int> maxToHere;
        vector<int> minToHere;
        maxToHere.push_back(nums[0]);
        minToHere.push_back(nums[0]);
        
        //找出每个以nums[i]结尾的最大积与最小积
        for(int i=1; i<nums.size(); ++i) {
            int cur = nums[i];
            maxToHere.push_back(max(cur, max(cur*maxToHere[i-1], cur*minToHere[i-1])));
            minToHere.push_back(min(cur, min(cur*maxToHere[i-1], cur*minToHere[i-1])));
        }
        
        //找出最大的数
        int max = maxToHere[0];
        for(int i=1; i<maxToHere.size(); ++i) {
            if(maxToHere[i] > max)  max = maxToHere[i];
        }
        
        return max;
    }
};