将具有20个数组元素的整型数组的前10个数升序排列，后10个降序排列。后续部分排序为什么乱套了


//将具有20个数组元素的整型数组的前10个数升序排列，后10个降序排列。
#include 
main()
{
    int a[20], trans, smlr, bigr;
    for (int i = 0; i < 20; i++)
        scanf_s("%d", &a[i]);
    for (int old = 0; old < 10; old++)
    {
        smlr = old;
        for (int new = 1 + old; new < 10; new++)
            if (a[new] < a[old])
                smlr = new;
        if (smlr != old)
        {
            trans = a[old];
            a[old] = a[smlr];
            a[smlr] = trans;
        }
    }
    for (int old = 10; old < 20; old++)
    {
        bigr = old;
        for (int new = 1 + old; new < 20; new++)
            if (a[new] > a[old])
                bigr = new;
        if (bigr != old)
        {
            trans = a[old];
            a[old] = a[bigr];
            a[bigr]=trans;
        }
    }
    for (int i = 0; i < 20; i++)
        printf("%d ", a[i]);
}

调试结果：
1
2
3
4
5
6
7
8
9
0
12
13
11
15
10
14
16
17
18
19
0 1 2 3 4 5 6 7 8 9 19 18 12 17 11 15 16 14 13 10
D:\Files\vs\test1\x64\Debug\test1.exe (进程 17308)已退出，代码为 0。
按任意键关闭此窗口. . .

if (a[new] < a[old])
应该是if (a[smlr] < a[old])
if (a[new] > a[old])
应该是
if (a[bigr] > a[old])
你的输入数据太整齐了，导致前半部分不需要怎么排就是有序的，你换个数据，前半部分也是乱的

img

因为你每一次做比较的都是第一个数，故而相当于第一个数和最靠后且比它大的数做交互（并不是最大的）

改动处见注释，供参考：

#include <stdio.h>
int main()    //修改 int 
{
    int a[20], trans, smlr, bigr;
    for (int i = 0; i < 20; i++)
        scanf_s("%d", &a[i]);
    for (int old = 0; old < 10 - 1; old++)  //(int old = 0; old < 10; old++)
    {
        smlr = old;
        for (int New = 1 + old; New < 10; New++) //new 改成 New 
            if (a[New] < a[smlr])  //if (a[New] < a[old])
                smlr = New;
        if (smlr != old)
        {
            trans = a[old];
            a[old] = a[smlr];
            a[smlr] = trans;
        }
    }
    for (int old = 10; old < 20 - 1; old++) //(int old = 10; old < 20; old++)
    {
        bigr = old;
        for (int New = 1 + old; New < 20; New++) //new 改成 New 
            if (a[New] > a[bigr]) //if (a[New] > a[old])
                bigr = New;
        if (bigr != old)
        {
            trans = a[old];
            a[old] = a[bigr];
            a[bigr] = trans;
        }
    }
    for (int i = 0; i < 20; i++)
        printf("%d ", a[i]);
    return 0;
}