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Copy pathQuickSort.java
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71 lines (61 loc) · 1.98 KB
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import annotations.Star;
@Star("快排的实现代码，注意可以优化，例如选取pivot时，可以随机或者三者取中")
public class QuickSort {
int [] nums;
public int[] sortArray(int[] nums) {
quicksort(nums,0, nums.length - 1);
return nums;
}
private void quicksort1(int left, int right) {
if (left >= right) {
return;
}
int oldLeft=left;
int oldRight = right;
//记录最左侧的元素下表
int pivot = nums[left];
while (left < right) {
//从right开始找第一个小于pivot的元素
while (left < right && nums[right] >= pivot) {
right--;
}
//找到后，放到left的指向
nums[left++] = nums[right];
while (left < right && nums[left] <= pivot) {
left++;
}
nums[right--] = nums[left];
}
nums[left] = pivot;
quicksort1(oldLeft, left - 1);
quicksort1(left + 1, oldRight);
}
private void quicksort(int []arr,int left, int right) {
if(left>=right) return;
int tar=arr[left+(int)(Math.random()*(right-left+1))];//不能传入mid索引 荷兰国旗必须用值
int [] border=partition(arr,tar,left,right);
quicksort(arr, left, border[0]-1);
quicksort(arr, border[1]+1, right);
}
private int[] partition(int[] arr, int tar,int left,int right) {
int less=left;
int more=right;
int index=left;
while (index<=more){
if(arr[index]<tar){
swap(arr, less++, index++);
}else if(arr[index]==tar){
index++;
}else {
swap(arr, index, more--);
}
}
return new int[]{less, more};
}
private void swap(int[] arr, int index, int i) {
int temp = arr[index];
arr[index] = arr[i];
arr[i]=temp;
}
//荷兰国旗升级版本
}