628. Maximum Product of Three Numbers

Posted 2020-10-31 一日一更

Given an integer array, find three numbers whose product is maximum and output the maximum product.

Example 1:

Input: [1,2,3]
Output: 6

 

Example 2:

Input: [1,2,3,4]
Output: 24

 

Note:

1. The length of the given array will be in range [3,104] and all elements are in the range [-1000, 1000].
2. Multiplication of any three numbers in the input won‘t exceed the range of 32-bit signed integer.

 

解题思路：

　　排序后两种情况，3个都是正数最大，2个是负数最小，一个是正数最大比大小。

　　

1. class Solution {  
2. public:  
3.     int maximumProduct(vector<int>& nums) {  
4.           
5.         if(nums.size()<3) return 0;  
6.         if(nums.size()==3) return nums[0]*nums[1]*nums[2];  
7.         int max_product=1;  
8.         int max_neg=1;  
9.         int n =nums.size();  
10.         sort(nums.begin(),nums.end());  
11.           
12.         if(nums[n-3]>=0)  
13.         max_product = nums[n-3]*nums[n-2]*nums[n-1];  
14.           
15.         if(nums[1]<=0)  
16.             max_neg=nums[0]*nums[1]*nums[n-1];  
17.           
18.         return max_product>=max_neg?max_product:max_neg;  
19.           
20.           
21.     }  
22. };