215. Kth Largest Element in an A

利用快排的思想求解数组中第K大的元素.
类似二分查找的思路，
需要注意的是，划分数组的时候，需要将左边改为大于pivot的值

class Solution:
    def findKthLargest(self, nums: List[int], k: int) -> int:
        if k > len(nums) or len(nums) < 1:
            return -1
        left = 0
        right = len(nums)-1
        while 1:
            mid = self.partition(nums, left, right)
            # print('left,right,mid', left,right,mid)
            if mid == k-1:
                return nums[mid]
            elif mid > k-1:
                right = mid - 1
            else:
                left = mid + 1
        return -1
            
        
    
    def partition(self, nums, start, end):
        pivot = nums[end]
        i = start
        for j in range(start, end):
            if nums[j] > pivot:
                nums[j], nums[i] = nums[i], nums[j]
                i += 1
        nums[i], nums[end] = nums[end], nums[i]
        return i