[刷题] PTA 6-11 求自定类型元素序列的中位数 (25分)

采用希尔排序

 1 #include <stdio.h>
 2
 3 #define MAXN 10
 4 typedef float ElementType;
 5
 6 ElementType Median( ElementType A[], int N );
 7
 8 int main ()
 9 {
10     ElementType A[MAXN];
11     int N, i;
12
13     scanf("%d", &N);
14     for ( i=0; i<N; i++ )
15         scanf("%f", &A[i]);
16     printf("%.2f\n", Median(A, N));
17
18     return 0;
19 }
20
21 ElementType Median( ElementType A[], int N ){
22     int h = 1;
23     while( h < N/2 )
24         h = 2 * h + 1;
25     while( h >= 1 ){
26         for( int i = h ; i < N ; i ++ ){
27             ElementType e = A[i];
28             int j;
29             for( j = i ; j >= h && e < A[j-h] ; j -= h )
30                 A[j] = A[j-h];
31             A[j] = e;
32         }
33         h /= 2;
34     }
35     return A[N/2];
36 }

• 希尔排序比常用的O（n^2）排序要快，采用其他排序算法会超时
• 间隔可任意设置
• 返回A[N/2]