49 lines
986 B
Go
49 lines
986 B
Go
package top100liked
|
|
|
|
import (
|
|
"math/rand"
|
|
"testing"
|
|
)
|
|
|
|
// https://leetcode.cn/problems/kth-largest-element-in-an-array/?envType=study-plan-v2&envId=top-100-liked
|
|
|
|
func findKthLargest(nums []int, k int) int {
|
|
n := len(nums)
|
|
target := n - k // 第 k 大 = 升序第 n-k 位
|
|
var quickSelect func(l, r int) int
|
|
quickSelect = func(l, r int) int {
|
|
if l == r {
|
|
return nums[l]
|
|
}
|
|
pivot := nums[l+rand.Intn(r-l+1)]
|
|
// 三路分区：[l..lt-1] < pivot, [lt..gt] == pivot, [gt+1..r] > pivot
|
|
lt, gt, i := l, r, l
|
|
for i <= gt {
|
|
switch {
|
|
case nums[i] < pivot:
|
|
nums[lt], nums[i] = nums[i], nums[lt]
|
|
lt++
|
|
i++
|
|
case nums[i] > pivot:
|
|
nums[gt], nums[i] = nums[i], nums[gt]
|
|
gt--
|
|
default:
|
|
i++
|
|
}
|
|
}
|
|
switch {
|
|
case target < lt:
|
|
return quickSelect(l, lt-1)
|
|
case target > gt:
|
|
return quickSelect(gt+1, r)
|
|
default:
|
|
return pivot
|
|
}
|
|
}
|
|
return quickSelect(0, n-1)
|
|
}
|
|
|
|
func Test(t *testing.T) {
|
|
findKthLargest([]int{3, 2, 1, 5, 6, 4}, 2)
|
|
}
|