获取数组中最小的K个数,利用堆完成。
public class MinKNum {
public void createHeap(int[]heap){
int len = heap.length;
int i = len >> 1;
while(i >= 1){
sink(heap,i);
i--;
}
}
public void sink(int[]heap,int i){
int len = heap.length;
int lChild = i << 1;
if (lChild >= len)
return;
int rChild = i << 1 + 1;
int next;
if (rChild >= len) {
next = lChild;
} else {
next = heap[lChild] >= heap[rChild] ? lChild:rChild;
}
if (heap[i] < heap[next]) {
swap(heap,i,next);
sink(heap,next);
}
}
public void swap(int[]heap,int i,int j){
int tmp = heap[i];
heap[i] = heap[j];
heap[j] = tmp;
}
public int[] getMinTopK(int[]array,int k){
int len = array.length;
if(len<=k){
return array;
}
int[] heap = new int[k+1];
for(int i=0;i<k;i++){
heap[i+1] = array[i];
}
createHeap(heap);
for(int i=k;i<len;i++){
if(heap[1]>array[i]){
heap[1] = array[i];
sink(heap,1);
}
}
return heap;
}
public static void main(String[]args){
MinKNum minKNum = new MinKNum();
int[] tops = minKNum.getMinTopK(new int[]{1,98,12,32,15,54,26,97,19,32,12},5);
for(int n:tops){
System.out.println(n);
}
}