java堆排，记录一下。（选择排序，时间复杂度O(n*logn),不稳定排序）
public void heapSort(int[] arr) {
int arrLength = arr.length;
for(int i = 0;i<arrLength-1;i++){
int lastIndex = arrLength-1-i;
buildMaxHeap(arr,lastIndex);
swap(arr,0,lastIndex);
}
}
public void buildMaxHeap(int[] arr,int lastIndex){
for(int i = (lastIndex-1)/2;i>=0;i--){
int k = i;
while(k*2+1<=lastIndex){
int biggerIndex = 2*k+1;
if(biggerIndex<lastIndex){
if(arr[biggerIndex]<arr[biggerIndex+1]){
biggerIndex++;
}
}
if(arr[k]<arr[biggerIndex]){
swap(arr,k,biggerIndex);
k = biggerIndex;
}else{
break;
}
}
}
}