[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

#include <stdio.h>

#define MAXN 10
typedef float ElementType;

ElementType Median( ElementType A[], int N );

int main ()
{
    ElementType A[MAXN];
    int N, i;

    scanf("%d", &N);
    for ( i=0; i<N; i++ )
        scanf("%f", &A[i]);
    printf("%.2f
", Median(A, N));

    return 0;
}

ElementType Median( ElementType A[], int N ){
    int h = 1;
    while( h < N/2 )
        h = 2 * h + 1;
    while( h >= 1 ){
        for( int i = h ; i < N ; i ++ ){
            ElementType e = A[i];
            int j;
            for( j = i ; j >= h && e < A[j-h] ; j -= h )
                A[j] = A[j-h];
            A[j] = e;
        }
        h /= 2;
    }
    return A[N/2];
}

• 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]