题目原址
https://leetcode.com/problems/maximum-product-subarray/description/
题目描述
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.
Example2:
Input: [-2,0,-1]
Output: 0
Explanation: The result cannot be 2, because [-2,-1] is not a subarray.
解题思路
找到给定数组中,连续数字的最大乘积。
这是一道动态规划,所以首先要明确,当前的最大乘积与前面数组中元素的乘积可能有关系,但是需要注意,这里还需要保存当前元素前面的元素的最小乘积。如{3,-1,-100},在这种情况下,最大的乘积为300。所以这里可以明确,需要两个变量来保存数组中元素的乘积:max
和localMin
,max用来存储当前的最大值,localMin用来存储当前最小值。
AC代码
class Soluti,blic int maxProduct(int[] nums) {
if(nums == null || nums.length == 0)
return 0;
int localMin = nums[0];
int max = nums[0];
int ret = nums[0];
for(int i = 1; i < nums.length; i++) {
int a = Math.max(Math.max(nums[i], max * nums[i]),localMin * nums[i]);
int b = Math.min(Math.min(nums[i], max * nums[i]),localMin * nums[i]);
if(a > ret)
ret = a;
if(b > ret)
ret = b;
max = a;
localMin = b;
}
return ret;
}
}