leetcode215:Kth Largest Element in an Array

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思路：参考TopK的Quick Select做法https://blog.csdn.net/Somnus_k/article/details/82724704

代码：

public class KthLargestElementinanArray {

	public static void main(String[] args) {
		int[] arr = { 1, 8, 35, 4, 7 };
		System.out.println(findKthLargest(arr, 4));
	}

	public static int findKthLargest(int[] nums, int k) {
		
		return quickSelect(nums,k,0,nums.length-1);
	}

	private static int quickSelect(int[] nums, int k, int i, int j) {
		if(i>=j)
			return nums[i];
		int index = partion(nums,i,j);
		if(index-i+1==k)
			return nums[index];
		else if(index-i+1>k)
			return quickSelect(nums, k, i, index-1);
		else
			return quickSelect(nums, k-(index-i+1), index+1, j);
	}

	private static int partion(int[] nums, int i, int j) {
		
		int tmp = nums[i];
		while(i<j){
			while(i<j)
				if(nums[j]>tmp)
				{
					nums[i]=nums[j];
					i++;
					break;
				}else
					j--;
			while(i<j)
				if(nums[i]<tmp)
					{
					nums[j]=nums[i];
					j--;
					break;
					}else
						i++;
		}
		nums[i]=tmp;
		return i;
	}

}

输出：