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

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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

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进步之处， 处理EPS 问题， 代码在后面

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#include<stdio.h>#include<string.h>#define EPS 1e-5const 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