返回数据流中的第K大元素

class KthLargest {

	private int[] minHeap;

	private final int k;

	private int last;

    public KthLargest(int k, int[] nums) {
    	this.k = k;
    	this.minHeap = new int[k];
    	this.last = -1;

    	for (int i=0;i<k&&i<nums.length;i++){
    		minHeap[i]=nums[i];
    		last = i;
    	}
    	if (last==k-1){
    		for (int j=(k-1)/2;j>=0;j--){
    			sink(j);
    		}
    		for (int j=last+1;j<nums.length;j++){
    			add(nums[j]);
    		}
    	}

    }

    private void sink(int i){
    	while(2*i+1<k){
    		int j = 2*i+1;
    		if (j<k-1&&minHeap[j]>minHeap[j+1]){
    			j++;
    		}
    		if (minHeap[i]>minHeap[j]){
    			int tem = minHeap[i];
    			minHeap[i]=minHeap[j];
    			minHeap[j]=tem;
    			i=j;
    		}else{
    			break;
    		}
    	}
    	
    }
    public int add(int val) {
    	if (last==k-2){
    		minHeap[k-1]=val;
    		last++;
    		for (int j=(k-1)/2;j>=0;j--){
    			sink(j);
    		}
    	}else{
    		if (val>minHeap[0]){
    			minHeap[0]=val;
    			sink(0);
    		}
    	}
        return minHeap[0];

    }
}