桶式排序是对一个有n个整型元素的数组a[n],其中对任意i,0 <= a[i] <= m的特殊排序算法。
可以对 n==m, n != m分别处理。写代码时需要注意的的是a[i]是访问第i-1个元素,而非第i个。
1![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
/**//************************************************************************************/
2![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
/**//* Bucket_Sort.h 桶式排序算法 */
3![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
/**//* 问题:对一个有n个整型元素a[0],a[1],…,a[n-1]的数组排序,其中0 <= a[i] <= m,任意i */
4![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
/**//* 程序:运行时间为O(m+n),辅助空间为O(m) */
5![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
/**//* 当 n=m 时特殊处理,运行时间为O(N), 辅助空间为O(1) */
6![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
/**//************************************************************************************/
7![](http://www.cppblog.com/Images/OutliningIndicators/None.gif)
8
#include <vector>
9![](http://www.cppblog.com/Images/OutliningIndicators/None.gif)
10![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
/**//*m != n */
11
void Bucket_Sort_m(int *a, int n, int m)
12![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
![](http://www.cppblog.com/Images/OutliningIndicators/ContractedBlock.gif)
{
13
std::vector<int> temp(m,0);
14
int i;
15
for(i = 0; i != n; ++i) //遍历a[]
16
++temp[a[i]-1]; //如果有对应于下标的值,标记为1,否则为0
17![](http://www.cppblog.com/Images/OutliningIndicators/InBlock.gif)
18
i = 0;
19
for(int j = 1; j <= m; ++j) //遍历temp向量
20
if(temp[j-1]) a[i++] = j;
21
22
temp.clear();
23
}
24![](http://www.cppblog.com/Images/OutliningIndicators/None.gif)
25![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
/**//* m == n */
26![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
/**//* 最后的结果是a[i-1] = i */
27
void Bucket_Sort(int *a,int n)
28![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
![](http://www.cppblog.com/Images/OutliningIndicators/ContractedBlock.gif)
{
29
for(int i = 1; i <= n; ++i)
30![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
{
31
while(a[i-1] != i)
32![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
{
33
int temp = a[a[i-1]-1];
34
a[a[i-1]-1] = a[i-1];
35
a[i-1] = temp;
36
}
37![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
/**//* 伪代码:如果假设可以通过a[i]访问数组的第i个元素,而不是第i-1个 */
38![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
/**//*while(a[i] != i)
39
{
40
int temp = a[a[i]];
41
a[a[i]] = a[i];
42
a[i] = temp;
43
}
44
*/
45
}
46
}