[LeetCode] Maximum Product of Three Numbers

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.

将数组按照逆序排序后，如果数组元素都是整数，则结果为前三个数的积，如果数组中存在负数，则判断数组前三个数之积与数字第一个数（最大正数）与数组最后两个负数之积。

class Solution {
public:
    int maximumProduct(vector<int>& nums) {
        sort(nums.begin(), nums.end(), [](int a, int b) {return a > b;});
        int n = nums.size();
        int res1 = nums[0] * nums[1] * nums[2];
        int res2 = nums[0] * nums[n - 1] * nums[n - 2];
        return max(res1, res2);
    }
};
// 72 ms