UVA

题目来源：https://cn.vjudge.net/problem/UVA-12412//题目太长不想复制

题意:

写一个学生成绩管理系统 (SPMS).

SID:10位数字

CID:不超过20的整数

name:不超过10位的一个字符串

four scores(Chinese, Mathematics, English and Programming):不超过100的自然数

1 - Add 加入数据

2 - Remove 删除数据

3 - Query 查询数据

4 - Show ranking 没用的只是输出一行话

5 - Show Statistics 输出总数据

0 - Exit 退出系统

评析：

此题很坑很不错，平台里的学生人数是0的时候平均数是-nan，而交上去AC了的是0，证明可能没有此数据，而且还有考虑精度问题。

代码：

#include<bits/stdc++.h>double EPS = 1e-5;  using namespace std;map<string, int>existsid;//Id查找 map<string, vector<int> >existname;//姓名查找 map<int, int>rank1;//存排名 queue<int>already;struct student{int sumscore;string sid;int cid;string name;int score[4];friend bool operator <(student x, student y){if (x.sid.length() == y.sid.length())return x.sid<y.sid;else return x.sid.length()<y.sid.length();}friend ostream& operator<<(ostream& cout, student x){cout << x.sid << " " << x.cid << " " << x.name;for (int i = 0; i<4; i++){cout << " " << x.score[i];}printf(" %d %.2lf", x.sumscore, 1.0*x.sumscore / 4);return cout;}}st[205], input, temp;//学生成绩数据 struct ends{int sumstudent;int chpass, enpass, mathpass, programpass;int sumch, sumen, summath, sumprogram;int a[5];ends(){sumstudent = chpass = enpass = mathpass = programpass = sumch = sumen = summath = sumprogram = 0;a[0] = a[1] = a[2] = a[3] = a[4] = 0;}}sumend[25];//存3里的输出数据 void title()//每次一开始显示这个 {cout << "Welcome to Student Performance Management System (SPMS)." << endl;cout << endl;cout << "1 - Add" << endl;cout << "2 - Remove" << endl;cout << "3 - Query" << endl;cout << "4 - Show ranking" << endl;cout << "5 - Show Statistics" << endl;cout << "0 - Exit" << endl;cout << endl;}void cleardatabase()//清空 {int i;while (!already.empty()){already.pop();}for (i = 1; i <= 200; i++){already.push(i);}rank1.clear();existsid.clear();existname.clear();}void choose1(){cout << "Please enter the SID, CID, name and four scores. Enter 0 to finish." << endl;cin >> input.sid;if (input.sid == "0")return;cin >> input.cid >> input.name >> input.score[0] >> input.score[1] >> input.score[2] >> input.score[3];input.sumscore = input.score[0] + input.score[1] + input.score[2] + input.score[3];int t = 0;if (existsid[input.sid])cout << "Duplicated SID." << endl;else{//此处开始存统计数据 rank1[input.sumscore]++;sumend[0].sumstudent++;sumend[input.cid].sumstudent++;sumend[0].sumch += input.score[0];sumend[input.cid].sumch += input.score[0];sumend[0].summath += input.score[1];sumend[input.cid].summath += input.score[1];sumend[0].sumen += input.score[2];sumend[input.cid].sumen += input.score[2];sumend[0].sumprogram += input.score[3];sumend[input.cid].sumprogram += input.score[3];if (input.score[0] >= 60){sumend[0].a[++t]++;sumend[0].chpass++;sumend[input.cid].a[t]++;sumend[input.cid].chpass++;}if (input.score[1] >= 60){sumend[0].a[++t]++;sumend[0].mathpass++;sumend[input.cid].a[t]++;sumend[input.cid].mathpass++;}if (input.score[2] >= 60){sumend[0].a[++t]++;sumend[0].enpass++;sumend[input.cid].a[t]++;sumend[input.cid].enpass++;}if (input.score[3] >= 60){sumend[0].a[++t]++;sumend[0].programpass++;sumend[input.cid].a[t]++;sumend[input.cid].programpass++;}//统计结束 st[already.front()] = input;existsid[input.sid] = already.front();existname[input.name].push_back(already.front());already.pop();}choose1();}void choose2(){int sums=0;cout << "Please enter SID or name. Enter 0 to finish." << endl;cin >> input.sid;if (input.sid == "0")return;if (existsid[input.sid])//找到存在ID需要删除 {//开始统计数据 temp = st[existsid[input.sid]];sumend[0].sumstudent--;sumend[temp.cid].sumstudent--;int t = 0;sumend[0].sumch -= temp.score[0];sumend[temp.cid].sumch -= temp.score[0];sumend[0].summath -= temp.score[1];sumend[temp.cid].summath -= temp.score[1];sumend[0].sumen -= temp.score[2];sumend[temp.cid].sumen -= temp.score[2];sumend[0].sumprogram -= temp.score[3];sumend[temp.cid].sumprogram -= temp.score[3];if (temp.score[0] >= 60){sumend[0].a[++t]--;sumend[0].chpass--;sumend[temp.cid].a[t]--;sumend[temp.cid].chpass--;}if (temp.score[1] >= 60){sumend[0].a[++t]--;sumend[0].mathpass--;sumend[temp.cid].a[t]--;sumend[temp.cid].mathpass--;}if (temp.score[2] >= 60){sumend[0].a[++t]--;sumend[0].enpass--;sumend[temp.cid].a[t]--;sumend[temp.cid].enpass--;}if (temp.score[3] >= 60){sumend[0].a[++t]--;sumend[0].programpass--;sumend[temp.cid].a[t]--;sumend[temp.cid].programpass--;}sums+=1;already.push(existsid[input.sid]);rank1[temp.sumscore]--;//统计结束 existsid[temp.sid] = 0;//删除ID vector<int>::iterator it;for(it=existname[temp.name].begin();it!=existname[temp.name].end();it++)//同时找到并删除ID相关的一个姓名 {if(st[*it].sid==input.sid)break;}if(it!=existname[temp.name].end())existname[temp.name].erase(it);}if (existname[input.sid].size()>0)//找到姓名需要删除 {sums+=existname[input.sid].size();//继续统计数据修改 while (existname[input.sid].size()>0){sumend[0].sumstudent--;temp = st[existname[input.sid].back()];sumend[temp.cid].sumstudent--;int t = 0;sumend[0].sumch -= temp.score[0];sumend[temp.cid].sumch -= temp.score[0];sumend[0].summath -= temp.score[1];sumend[temp.cid].summath -= temp.score[1];sumend[0].sumen -= temp.score[2];sumend[temp.cid].sumen -= temp.score[2];sumend[0].sumprogram -= temp.score[3];sumend[temp.cid].sumprogram -= temp.score[3];if (temp.score[0] >= 60){sumend[0].a[++t]--;sumend[0].chpass--;sumend[temp.cid].a[t]--;sumend[temp.cid].chpass--;}if (temp.score[1] >= 60){sumend[0].a[++t]--;sumend[0].mathpass--;sumend[temp.cid].a[t]--;sumend[temp.cid].mathpass--;}if (temp.score[2] >= 60){sumend[0].a[++t]--;sumend[0].enpass--;sumend[temp.cid].a[t]--;sumend[temp.cid].enpass--;}if (temp.score[3] >= 60){sumend[0].a[++t]--;sumend[0].programpass--;sumend[temp.cid].a[t]--;sumend[temp.cid].programpass--;}already.push(existname[input.sid].back());rank1[temp.sumscore]--;//结束->此处省略千字(吐血身亡) existsid[temp.sid]=0;//删ID existname[temp.name].pop_back();//删姓名 }}cout << sums << " student(s) removed." << endl;choose2();}void choose3(){map<int, int>::iterator it;cout << "Please enter SID or name. Enter 0 to finish." << endl;cin >> input.sid;if (input.sid == "0")return;if (existsid[input.sid])//找到ID {int ls = 0, flag = 0;for (it = rank1.begin(); it != rank1.end(); it++){if (it->first == st[existsid[input.sid]].sumscore){flag = 1;}else if (flag){ls += it->second;}}cout << ls + 1 << " ";cout << st[existsid[input.sid]] << endl;}else if (existname[input.sid].size()>0)//找到姓名 {for (int i = 0; i<existname[input.sid].size(); i++){int ls = 0, flag = 0;for (it = rank1.begin(); it != rank1.end(); it++){if (it->first == st[existname[input.sid][i]].sumscore){flag = 1;}else if (flag){ls += it->second;}}cout << ls + 1 << " ";cout << st[existname[input.sid][i]] << endl;}}choose3();}void choose4(){cout << "Showing the ranklist hurts students' self-esteem. Don't do that." << endl;}void choose5(){int cl;//终于输出数据了 cout << "Please enter class ID, 0 for the whole statistics." << endl;cin >> cl;cout << "Chinese" << endl;cout << "Average Score: "; printf("%.2lf\n", sumend[cl].sumstudent==0?0:sumend[cl].sumch*1.0 / sumend[cl].sumstudent+EPS);cout << "Number of passed students: " << sumend[cl].chpass << endl;cout << "Number of failed students: " << sumend[cl].sumstudent - sumend[cl].chpass << endl;cout << endl;cout << "Mathematics" << endl;cout << "Average Score: "; printf("%.2lf\n", sumend[cl].sumstudent==0?0:sumend[cl].summath*1.0 / sumend[cl].sumstudent+EPS);cout << "Number of passed students: " << sumend[cl].mathpass << endl;cout << "Number of failed students: " << sumend[cl].sumstudent - sumend[cl].mathpass << endl;cout << endl;cout << "English" << endl;cout << "Average Score: "; printf("%.2lf\n", sumend[cl].sumstudent==0?0:sumend[cl].sumen*1.0 / sumend[cl].sumstudent+EPS);cout << "Number of passed students: " << sumend[cl].enpass << endl;cout << "Number of failed students: " << sumend[cl].sumstudent - sumend[cl].enpass << endl;cout << endl;cout << "Programming" << endl;cout << "Average Score: "; printf("%.2lf\n", sumend[cl].sumstudent==0?0:sumend[cl].sumprogram*1.0 / sumend[cl].sumstudent+EPS);cout << "Number of passed students: " << sumend[cl].programpass << endl;cout << "Number of failed students: " << sumend[cl].sumstudent - sumend[cl].programpass << endl;cout << endl;cout << "Overall:" << endl;cout << "Number of students who passed all subjects: " << sumend[cl].a[4] << endl;cout << "Number of students who passed 3 or more subjects: " << sumend[cl].a[3] << endl;cout << "Number of students who passed 2 or more subjects: " << sumend[cl].a[2] << endl;cout << "Number of students who passed 1 or more subjects: " << sumend[cl].a[1] << endl;cout << "Number of students who failed all subjects: " << sumend[cl].sumstudent-sumend[cl].a[1] << endl;cout << endl;}int main(){cleardatabase();int choose;while (1){title();cin >> choose;if (choose == 0)break;else if (choose == 1)choose1();else if (choose == 2)choose2();else if (choose == 3)choose3();else if (choose == 4)choose4();else if (choose == 5)choose5();}}