程序代码：

#include <iostream>
#include <cstdlib>
int s[1000001];
int partition(int *a, int len)
{
    int i, j = 0;
    std::swap(a[0], a[rand() % len]);
    for (i = 1; i < len; ++i)
        if (a[i] > a[0]) ++j, std::swap(a[i], a[j]);
    std::swap(a[0], a[j]);
    return j;
}
int quick_select(int *a, int len, int i)
{
    int k = partition(a, len);
    if (k == i) return a[k];
    return k > i ? quick_select(a, k, i)
           : quick_select(&a[k + 1], len - k - 1, i - k - 1);
}
int main(void)
{
    int i, n, k;
    while (scanf("%d%d", &n, &k) == 2)
    {
        for (i = 0; i < n; ++i)
            scanf("%d", &s[i]);
        printf("%d\n", quick_select(s, n, k - 1));
    }
    return 0;
}

程序代码：

/* VC 环境 */
#include <stdio.h>
#include <stdlib.h>

int main (void)
{
    int numStud;
    int i;
    int first  = 0;
    int second = 0;
    int third  = 0;
    int count  = 0;
    int a[100];
    int *ary;

    //输入同学人数
    do
    {
        printf("Number of Student: ");
        scanf("%d", &numStud);
        //限制人数范围，违规循环
        if(numStud < 0 || numStud > 10000)
            printf("Error Input Students' Number!\n");
    }while(numStud < 0 || numStud > 10000);

    //如果不是键入0
    while(numStud != 0)
    {  
        //准备储存空间
        ary = (int*)malloc(numStud*sizeof(ary));

        //输入同学的分数存入数组
        for(i = 0; i < numStud; i++)
        {
            do
            {
                printf("Mark of Student %d: ", i + 1);
                scanf("%d", &ary[i]);
                //限制分数范围，违规循环
                if(ary[i] < 0 || ary[i] > 100)
                    printf("Error Input Mark!\n");
            }while(ary[i] < 0 || ary[i] > 100);
        }//end for


        printf("\n");


        //寻找最高分
        for(i = 0; i < numStud; i++)
            if(ary[i] > first)
                first = ary[i];

        //找最高分，然后与第一高分比较，小者得次高
        for(i = 0; i < numStud; i++)
            if(ary[i] > second && ary[i] < first)
                second = ary[i];

        //找最高分，然后与第二高分比较，小者是第三
        for(i = 0; i < numStud; i++)
            if(ary[i] > third && ary[i] < second)
                third = ary[i];

        //清除数据之前，将第三高分赋值给另一数组
        //如果没有第三高分，这里的third其实是第二高分，赋值0以方便输出那个no such score
        if(third == second)
            a[count] = -1;
        else a[count] = third;

        count++;//计算循环次数

        //清除数组数据
        free(ary);

        //还有其他组要输入的话，这里输入同学人数，输入0可结束循环看结果
        do
        {
            printf("Number of Student: ");
            scanf("%d", &numStud);
            //限制输入范围，违规循环
            if(numStud < 0 || numStud > 10000)
                printf("Error Input!\n");
        }while(numStud < 0 || numStud > 10000);


    }//end while


    //结果输出
    printf("\n\nThe Third Student's Mark: \n");
    for(int i = 0; i < count; i++)
    {
        if(a[i] == 0)
            printf("No such Score!\n\n");
        else printf("%d\n",a[i]);
    }
    
    return 0;
}

程序代码：

#include"stdio.h"
void li(int a[],int p)
{
    int i,j,m=0,t;
    for(i=1;i<=p;i++)
        scanf("%d",&a[i]);
    for(j=0;(j<=p-1)&&(m<2);j++)
    {    for(i=p;i>j+1;i--)
            if(a[i]>a[i-1])
            {
                t=a[i-1];
                a[i-1]=a[i];
                a[i]=t;
            }
            a[0]=a[1];
            if(a[j]!=a[j+1])
                m++;
    }
    if(m==2)
            printf("第三名成绩：%d\n",a[j]);
    else 
        printf("no");
}
            
 main()
{
    int x[50],p;
    printf("请输入人数:\n");
    scanf("%d",&p);
    while(p!=0)
    {
        li(x,p);
        printf("\n");
           scanf("%d",&p);
    }
    return 0;
}