152. Maximum Product Subarray（js）

152. Maximum Product Subarray

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.

题意：给定一个数字数组（包含正数，负数和零），求连续子数组项的乘积的最大值
代码如下：

/**
 * @param {number[]} nums
 * @return {number}
 */
var maxProduct = function(nums) {
    let mx=nums[0];
    let mn=nums[0];
    let res=nums[0];
    
    for(let i=1;i<nums.length;i++){
//         max:数组前i+1项的最大乘积
//         min:数组前i+1项的最小乘积
//         dp思想，不断比较之前数组项的最小值*当前项，当前项，之前数组项的最大值*当前项，并不断更新最大值
        let max=mx,min=mn;
        mx=Math.max(Math.max(min*nums[i],nums[i]),max*nums[i]);
        mn=Math.min(Math.min(max*nums[i],nums[i]),min*nums[i]);
        res=Math.max(res,mx);
    }
    return res;
};