LeetCode-152-Maximum Product Subarray

标签：use   最小值   which   input   vector   return   inpu   情况   ges   

算法描述：

Given an integer array nums, find the contiguous subarray within an array (containing at least one number) which has the largest product.

Example 1:

Input: [2,3,-2,4]
Output: 6
Explanation: [2,3] has the largest product 6.

Example 2:

Input: [-2,0,-1]
Output: 0
Explanation: The result cannot be 2, because [-2,-1] is not a subarray.

解题思路：用动态规划求解。最小值（最大值）分三种情况：当前值，当前值乘以前一个最小值（最大值），以及当前值乘以前一个最大值（最小值）。递推式为：

minVale[i] = min(min(nums[i],nums[i]*maxValue[i-1]),nums[i]*minValue[i-1]);

maxVale[i] = max(max(nums[i],nums[i]*maxValue[i-1]),nums[i]*minValue[i-1]);

内存空间还可以压缩。

    int maxProduct(vector<int>& nums) {
        if(nums.size()==0) return 0;
        if(nums.size()==1) return nums[0];
        vector<int> minVal(nums.size(),0);
        vector<int> maxVal(nums.size(),0);
        
        minVal[0] = min(nums[0],0);
        maxVal[0] = max(nums[0],0);
        
        int res = maxVal[0];
        
        for(int i=1; i < nums.size(); i++){
            minVal[i] = min(min(nums[i], nums[i]*maxVal[i-1]),minVal[i-1]*nums[i]);
            maxVal[i] = max(max(nums[i], nums[i]*minVal[i-1]),maxVal[i-1]*nums[i]);
            if(res < maxVal[i])
                res = maxVal[i];
        }
        return res;
    }

LeetCode-152-Maximum Product Subarray

标签：use   最小值   which   input   vector   return   inpu   情况   ges   

原文地址：https://www.cnblogs.com/nobodywang/p/10354495.html