快速排序思想:
基于分治策略,对冒泡排序的一种改进。对于要排序的一个序列,从中选一值进行排序,将其放入到正确的位置position。然后以position为界,对左右两部分再做排序。直到划分的长度为1。
步骤:设有一待排序的序列
1.分别设置low、hight指向序列的最左端、最右端;从序列中选一个进行排序(通常选最左端的值low指向的值),存入到tmp;
2.从hight端开始,查找比tmp小的,找到后讲该值放入到low指向的存储位中;同时将hight指向当前查到的值所在的位;
3.从low端开始,查找比tmp大的,找到后将该值放入到hight指向的存储为中,同时low指向当前查到的值所在位;
4.若low位小于hight位,返回2步;否则,将tmp值存入到空出来的low+1指向的位置,退出,返回low所在的位置lposition。
5.以lposition为界,将序列分成两部分,分别对两部分进行排序。
这里用个整数数组作为待排序的序列,c#实现如下:
![](https://www.cnblogs.com/Images/OutliningIndicators/ContractedBlock.gif)
快速排序
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/**//* 快速排序
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** 作者:huankfy
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** 时间:2009-04-29
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*/
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public class MyQuickSort
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{
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int[] data = new int[]
{ 10, 2, 5, 7, 3, 1, 20, 34, 4, 6, 30, 100, 23, 8 };
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public void Display()
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{
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Sort(data, 0, data.Length - 1);
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Console.WriteLine("快速排序结果为:");
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for (int i = 0; i < data.Length; i++)
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Console.WriteLine(data[i]);
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}
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private void Sort(int[] a, int left, int right)
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{
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if (left < right)
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{
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int i = Partition(a, left, right);
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Sort(a, left, i - 1);
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Sort(a, i + 1, right);
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}
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}
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private int Partition(int[] a, int left, int right)
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{
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int tmp = a[left];
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while (left < right)
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{
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while (left < right && a[right] >= tmp)
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right--;
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// 换位后不能将left+1,防止跳位
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if(left<right)
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a[left] = a[right];
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while (left < right && a[left] <= tmp)
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left++;
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if (left < right)
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{
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a[right] = a[left];
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// 有left < right,可将right向前推一位
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right--;
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}
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}
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a[left] = tmp;
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return left;
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}
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}
其中最关键的是Partition,做一次排序的划分,将其放入到正确的位置。
注:已在vs2005中编译通过,并正确执行。