Kth Largest Element in an Array

Find the kth largest element in an unsorted array. Note that it is the kth largest element in the sorted order, not the kth distinct element.

For example,
Given [3,2,1,5,6,4] and k = 2, return 5.

Note: 
You may assume k is always valid, 1 ≤ k ≤ array‘s length.

Credits:
Special thanks to @mithmatt for adding this problem and creating all test cases.

算法：

最小堆排序

public class Solution {
    public int findKthLargest(int[] nums, int k) {
		int[] b = new int[k];
		for (int i = 0; i < k; i++) {
			b[i] = nums[i];
		}
		for(int i=b.length/2;i>=0;i--){
			minHeapSort(b,i,b.length);
		}
		for (int i = k; i < nums.length; i++) {
			if (nums[i] > b[0]) {
				b[0] = nums[i];
				minHeapSort(b,0,b.length);
			}
		}
		return b[0];
	}

	private void minHeapSort(int[] b,int i, int n) {
		int tmp = b[i];
		int child;
		for (; i * 2 + 1 < n; i = child) {
			child = i * 2 + 1;
			if (child < n - 1 && b[child + 1] < b[child]) {
				child++;
			}
			if (tmp > b[child]) {
				b[i] = b[child];
			} else
				break;
		}
		b[i] = tmp;
	}
}

Kth Largest Element in an Array

原文：http://blog.csdn.net/u010786672/article/details/45936211