堆排序heapSort

堆排序

/** *堆排序：是利用完全二叉树特性的一种选择排序。 *时间复杂度O(nlog(2)n),空间复杂度O(1) *堆：根节点最大/小,对序列用于多次求极值的应用问题。如优先队列、Huffman、Prim、Kruskal、Dijkstra、Floyd等算法 * @author  * */public class heapSort {public static void heapSort(int[] keys){heapSort(keys,true);}public static void heapSort(int[] keys,boolean minheap){for(int i=keys.length/2-1;i>=0;i--) sift(keys,i,keys.length-1,minheap);//创建最小/最大堆，根结点值最小/大for(int i=keys.length-1;i>0;i--){ //将最小/最大值交换到最后，再调整成最小/最大堆swap(keys,0,i);sift(keys,0,i-1,minheap);}}private static void swap(int[] keys,int i,int j){int temp = keys[i];keys[i] = keys[j];keys[j] = temp;}private static void sift(int[] keys,int parent,int end,boolean minheap){//将以parent为根的子树调整为最小/最大堆，子序列范围parent~endint child = parent*2+1;int value = keys[parent];while(child<=end){ //沿孩子结点向下筛选if(child<end&&(minheap?keys[child]>keys[child+1]:keys[child]<keys[child+1])) child++;//标记孩子值较小/较大者if(minheap?value>keys[child]:value<keys[child]){//若父母结点值较小/较大keys[parent] = keys[child];//将较小/大孩子上移parent = child;//parent向下一层child = 2*parent+1;//child向下一层}else break;}keys[parent] = value;//当前子树的原根值调整后的位置}}