题解 | #最大乘积#

package main

import (
    "fmt"
)

//时间复杂度O(N*logN)
//空间复杂度O(1)
func main() {
    a := 0
    _, _ = fmt.Scan(&a)
    //fmt.Println(a)
    nums := make([]int, a)
    for i:=0; i < a; i++ {
        b := 0
        _, _ = fmt.Scan(&b)
        nums[i] = b
    }
   //fmt.Println(nums)
   quickSort(nums, 0, len(nums)-1)
   //fmt.Println(nums)
   //如果最大开始三个都是正数
   //最大前一个是正数 后面开始是负的最小两个数值
   //为0则跳过
   a = 0
   if len(nums) >= 3 && nums[0] > 0 && nums[1] > 0 && nums[2] > 0 {
        a = nums[0]*nums[1]*nums[2]
   }
   b := 0
   if len(nums) >= 3 && nums[len(nums)-1] < 0 && nums[len(nums)-2] < 0 && nums[0] > 0 {
        b = nums[len(nums)-1]  * nums[len(nums)-2] * nums[0]
   }
   if a > b {
   fmt.Println(a)
   }else {
        fmt.Println(b)
   }
}

func quickSort(nums []int, left ,right int) {
    if left >= right {
        return
    }
    p := getPartition(nums, left, right)
    quickSort(nums, left, p-1)
    quickSort(nums, p+1, right)
}

func getPartition(nums []int, left, right int) int {
    sentry := nums[right]
    i := left
    for j := left; j <= right; j++ {
        if nums[j] > sentry {
            nums[i], nums[j] = nums[j], nums[i]
            i++
        }
    }
    nums[i], nums[right] = sentry, nums[i]
    return i
}