UVA - 12412 A Typical Homework (a.k.a Shi Xiong Bang Bang Mang)

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算法入门经典第二版第四章函数与递归专栏收录该内容

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本文介绍了一个学生学业管理系统的实现，包括添加、删除、查询、展示排名和统计数据等功能。通过处理EPS问题，系统确保了数据的准确性。详细阐述了如何使用C语言进行系统开发，以及在实现过程中遇到的挑战和解决方法。

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看了书又看了网上的代码敲出来的，汗，自己敲是很难做出来的

进步之处，处理EPS 问题，代码在后面

#include<stdio.h>
#include<string.h>
#define EPS 1e-5
const int maxn = 1000;
const int maxl = 10 + 5;
int n;
int removed[maxn];
char sid[maxn][maxl];
int cid[maxn];
char name[maxn][maxl];
int score[maxn][5];
const char *course_name[]={"Chinese","Mathematics","English","Programming"};
void print_menu()
{
    printf("Welcome to Student Performance Management System (SPMS).\n");
    printf("\n");
    printf("1 - Add\n");
    printf("2 - Remove\n");
    printf("3 - Query\n");
    printf("4 - Show ranking\n");
    printf("5 - Show Statistics\n");
    printf("0 - Exit\n");
    printf("\n");
}

int valid(int k)
{
    for (int i=0;i<k;i++)
    {
        if(!removed[i])
        {
            if(!strcmp(sid[i],sid[k])) return 0;
        }
    }
    return 1;
}

void add()
{
    for(;;)
    {
        printf("Please enter the SID, CID, name and four scores. Enter 0 to finish.\n");
        scanf("%s",sid[n]);
        if(!strcmp(sid[n],"0")) break;
        scanf("%d%s%d%d%d%d",&cid[n],name[n],&score[n][0],&score[n][1],&score[n][2],&score[n][3]);
        if(valid(n))
        {
            score[n][4]=score[n][0]+score[n][1]+score[n][2]+score[n][3];
            n++;
        }
        else
            printf("Duplicated SID.\n");
    }
}
int rank(int k)
{
    int r=0;
    for(int i=0;i<n;i++)
    {
         if(!removed[i]&&score[i][4]>score[k][4]) r++;
    }
    return r+1;
}
void DQ (int isq)
{
    char s[maxl];
    for(;;)
    {
        printf("Please enter SID or name. Enter 0 to finish.\n");
        scanf("%s",s);
        if(!strcmp (s, "0"))
            break;
        int r=0;
        for(int i=0;i<n;i++)
            if(!removed[i])
            {
                if(!strcmp(sid[i],s)||!strcmp(name[i],s))
                {
                    if(isq)
                        printf("%d %s %d %s %d %d %d %d %d %.2f\n",rank(i),sid[i],cid[i],name[i],score[i][0],score[i][1],score[i][2],score[i][3],score[i][4],score[i][4]/4.0+EPS);
                    else
                    {
                        removed[i]=1;
                        r++;
                    }
                }
            }
        if(!isq)
            printf("%d student(s) removed.\n",r);
    }
}
double get_course_stat(int c,int s,int* passed,int* failed)
{
    int tot=0;
    *passed=*failed=0;
    for(int i=0;i<n;i++)
    {
        if(!removed[i]&&(!c||cid[i]==c))
        {
            tot+=score[i][s];
            if(score[i][s]>=60)
                (*passed)++;
            else
                (*failed)++;
        }
    }
    return (double)tot/(double)(*passed+*failed);
}
void get_overall_stat(int c,int* cnt)
{
    memset(cnt, 0, sizeof(cnt));
    for(int i=0;i<n;i++)
    {
        if(!removed[i]&&(!c||cid[i]==c))
        {
            int k=0;
            for(int j=0;j<4;j++)
            {
                if(score[i][j]>=60) k++;
            }
            cnt[k]++;
        }
    }
}
void stat()
{
    int c;
    printf("Please enter class ID, 0 for the whole statistics.\n");
    scanf("%d", &c);
    for(int i=0;i<4;i++)
    {
        int passed,failed;
        double avg=get_course_stat(c,i,&passed,&failed);
        printf("%s\n",course_name[i]);
        printf("Average Score: %.2f\n",avg+EPS);
        printf("Number of passed students: %d\n",passed);
        printf("Number of failed students: %d\n",failed);
        printf("\n");
    }
    int cnt[5];
    get_overall_stat(c,cnt);
    printf("Overall:\n");
    printf("Number of students who passed all subjects: %d\n",cnt[4]);
    printf("Number of students who passed 3 or more subjects: %d\n",cnt[4]+cnt[3]);
    printf("Number of students who passed 2 or more subjects: %d\n",cnt[4]+cnt[3]+cnt[2]);
    printf("Number of students who passed 1 or more subjects: %d\n",cnt[4]+cnt[3]+cnt[2]+cnt[1]);
    printf("Number of students who failed all subjects: %d\n",cnt[0]);
    printf("\n");
}
int main()
{
    for(;;)
    {
        int choice;
        print_menu();
        scanf("%d",&choice);
        if(choice==0) break;
        if(choice==1) add();
        if(choice==2) DQ(0);
        if(choice==3) DQ(1);
        if(choice==4) printf("Showing the ranklist hurts students' self-esteem. Don't do that.\n");
        if(choice==5) stat();
    }
    return 0;
}

EPS问题：

#include<stdio.h>
int main()
{
    double f;
    for(f = 2;  f > 1; f-= 1e-6);
    printf("%.7f\n", f);
    printf("%.7f\n", f/4);
    printf("%.1f\n", f/4);
    return 0;
}

输出：
0.9999990

0.2499998

0.2

在减1e-6的过程中有误差，所以一遍采取加上一个EPS输出， EPS通常比最低精度还要小几个数量级的小实数