# 堆排序

``````时间复杂度O(nlogn)
``````
``````import java.util.Arrays;

public class Code_03_HeapSort {
public static void heapSort(int []arr){
if(arr==null||arr.length<2){
return;
}
for (int i = 0; i < arr.length; i++) {
heapInsert(arr,i);
}
int size=arr.length;
swap(arr,0,--size);
while (size>0){
heapify(arr,0,size);
swap(arr,0,--size);
}
}

private static void heapInsert(int[] arr, int index) {
while (arr[index]>arr[(index-1)/2]){
swap(arr,index,(index-1)/2);
index=(index-1)/2;
}
}
private static void swap(int[] arr, int i, int j) {
int temp=arr[i];
arr[i]=arr[j];
arr[j]=temp;

}
private static void heapify(int[] arr, int index, int size) {
int left =index*2+1;
while (left<size){
int largest=left+1<size&&arr[left+1]>arr[left]?left+1:left;
largest=arr[largest]>arr[index]?largest:index;
if (largest==index){
break;
}
swap(arr,largest,index);
index=largest;
left=index*2+1;
}
}
public static void comparator(int []arr){
Arrays.sort(arr);
}

//for test
public static int []generateRandomArray(int maxSize,int maxValue){
int []arr=new int[(int)((maxSize+1)*Math.random())];
for (int i = 0; i < arr.length; i++) {
arr[i]=(int)((maxValue+1)*Math.random())-(int)((maxValue)*Math.random());

}
return arr;
}
//for test
public static int []copyArray(int []arr){
if(arr==null){
return null;
}
int []res=new int[arr.length];
for (int i = 0; i < arr.length; i++) {
res[i]=arr[i];

}
return res;

}
//for test
public static boolean isEqual(int []arr1,int []arr2){
if((arr1==null)&&(arr2!=null)||(arr1!=null&&arr2==null)){
return false;
}
if(arr1==null&&arr2==null){
return true;
}
if(arr1.length!=arr2.length){
return false;
}
for (int i = 0; i < arr1.length; i++) {
if(arr1[i]!=arr2[i]){
return false;
}

}
return  true;
}
public static void printArray(int []arr){
if(arr==null){
return;
}
for (int i = 0; i < arr.length; i++) {
System.out.print(arr[i]+" ");

}
System.out.println();
}

public static void main(String[] args) {
int testTime=50000;
int maxSize=100;
int maxValue=100;
boolean succeed=true;
for (int i = 0; i < testTime; i++) {
int []arr1=generateRandomArray(maxSize,maxValue);
int []arr2=copyArray(arr1);
heapSort(arr1);
comparator(arr2);
if (!isEqual(arr1,arr2)){
succeed=false;
printArray(arr1);
printArray(arr2);
break;
}
}
System.out.println(succeed?"Nicd !":"Fucking fucked!");

int []arr=generateRandomArray(maxSize,maxValue);
printArray(arr);
heapSort(arr);
printArray(arr);
}

}

``````
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