628. Maximum Product of Three Numbers 笔记

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.

求三个数能让这三个数乘积最大，返回最大的乘积。想先排序。挑最大的三个数，计算这仨数的乘积，还要考虑，可能有两个负的。那就再考虑最大数和最小的两个数的乘积。就比较一下这两个乘积那个大，就选哪个。

class Solution {
public:
    int maximumProduct(vector& nums) {
        sort(nums.begin(), nums.end());
        int r1 = nums[nums.size() - 1] * nums[nums.size() - 2] * nums[nums.size() - 3];
        int r2 = nums[0] * nums[1] * nums[nums.size() - 1];
        if(r1 > r2)
            return r1;
        else
            return r2;
    }
};