数组中的第K个最大元素

解题思路:

class Solution {
          
   
    public int findKthLargest(int[] nums, int k) {
          
   
        Arrays.sort(nums);
        return nums[nums.length - k];
    }
}

显然, 要用到的是快排

class Solution {
          
   
    public int findKthLargest(int[] nums, int k) {
          
   
        quickSort(nums, 0, nums.length - 1, k);
        return nums[nums.length - k];
    }
    public void quickSort(int[] nums, int left, int right, int k){
          
   
        int v = nums[right];
        int l = left;
        int r = right;
        while(l < r){
          
   
            while(l < r && nums[l] <= v){
          
   
                l++;
            }
            while(l < r && nums[r] >= v){
          
   
                r--;
            }
            if(l < r){
          
   
                int tmp = nums[l];
                nums[l] = nums[r];
                nums[r] = tmp;
            }
        }
        nums[right] = nums[r];
        nums[r] = v;
        if(r > nums.length - k){
          
   
            quickSort(nums, left, r - 1, k);
        }else if(r < nums.length - k){
          
   
            quickSort(nums, r + 1, right, k);
        }
    }
}