628. Maximum Product of Three Numbers

题目来源【Leetcode】

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:
The length of the given array will be in range [3,104] and all elements are in the range [-1000, 1000].
Multiplication of any three numbers in the input won’t exceed the range of 32-bit signed integer.

这道题主要是注意有负数的情况，先排序，然后如果头两个都是负数，就比较最后三个的积与前两个负数和最后一个数的积，不是的话就直接最后三个数的积最大

class Solution {
public:
    int maximumProduct(vector<int>& nums) {
        sort(nums.begin(),nums.end());
        int s = nums.size();
        if(nums[0] < 0 && nums[1] < 0) 
        return max(nums[0]*nums[1]*nums[s-1],nums[s-1]*nums[s-2]*nums[s-3]);
        else return  nums[s-1]*nums[s-2]*nums[s-3];

    }
};