P7911 [CSP-J 2021] 网络连接

属于是大模拟中非常良心的一道了（）

这一题的主要难点在于提取 $a,b,c,d,e$ 并判断前导 $0$ 和逗号，分号。

首先要介绍一个神器：sscanf(). 以本题为例子，假设我们用一个字符数组 $\texttt{newp}$ 存了一个地址串，想要从中提取 $a,b,c,d,e$，我们可以这样写：

int num = sscanf(place, "%lld.%lld.%lld.%lld:%lld", &a, &b, &c, &d, &e);`

其中，$\texttt{num}$ 表示从前往后成功读取到的字符数量。若 $\texttt{num} \ne 5$，那么 $\texttt{place}$ 显然不是一个合法的地址串，然后再判断 $a,b,c,d,e$ 的大小即可。

有 sscanf() 当然有 sprintf()，在本题中，我们可以以 $a,b,c,d,e$ 重新以标准格式构造一个地址串，输出到一个字符串中。若这个新地址串与原地址串完全相同，说明原地址串合法，否则不合法。

另外有几个小坑点：

• 输出的编号是所有机器的编号而非服务机的序号
• $a,b,c,d,e$ 如果用 %d 读取会炸
• 错误是输出 ERR 而非 ERROR

代码：

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstdlib>

using namespace std;

typedef long long ll;

const int N = 1010;

int n;
string server[N];

bool check(string s) {
    ll a = 0, b = 0, c = 0, d = 0, e = 0;
    const char* place; char newp[110];
    place = s.c_str(); 
    int num = sscanf(place, "%lld.%lld.%lld.%lld:%lld", &a, &b, &c, &d, &e);
    if (num != 5) return 0;
    sprintf(newp, "%lld.%lld.%lld.%lld:%lld", a, b, c, d, e);
    string ss = newp;
    if (ss != s) return 0;
    if (a < 0 || a > 255 || b < 0 || b > 255 || c < 0 || c > 255 || 
        d < 0 || d > 255 || e < 0 || e > 65535) return 0;
    return 1;
}

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0), cout.tie(0);

    cin >> n;
    string op, place;
    for (int i = 1; i <= n; ++i) {
        cin >> op >> place;
        if (!check(place)) {
            cout << "ERR" << endl;
            continue;
        }

        if (op == "Server") {
            bool flag = 0;
            for (int j = 1; j <= i; ++j) {
                if (place == server[j]) {
                    flag = 1;
                    cout << "FAIL" << endl;
                    break;
                }
            }
            if (!flag) {
                server[i] = place;
                cout << "OK" << endl;
            }
        }
        else {
            bool flag = 0;
            for (int j = 1; j <= i; ++j) {
                if (place == server[j]) {
                    flag = 1;
                    cout << j << endl;
                    break;
                }
            }
            if (!flag) cout << "FAIL" << endl;
        }
    }

    system("pause");
    return 0;
}

UVA12412 A Typical Homework (a.k.a 师兄帮帮忙)

所有操作都可以暴力完成。

开一个结构体 Student，存储 $\texttt{sid,uid,name}$，四科成绩及总分。用一个 vector 数组 $s$ 来存储所有学生。另外还可以开一个 unordered_map 来存储所有学生的 $\texttt{sid}$.

对于添加操作，先判断新学生的 $\texttt{sid}$ 是否重复，如果不是就添加到 $s$ 中。

对于删除操作，遍历 $s$ 数组，若 $s_i.\texttt{sid}$ 或 $s_i.\texttt{name}$ 与输入的字符串相匹配，则用 erase 函数将其删去。（这里有一个坑点，详见代码）

对于查询操作，几乎和删除操作一样，遍历 $s$ 数组，若 $s_i.\texttt{sid}$ 或 $s_i.\texttt{name}$ 与输入的字符串相匹配，则计算其各项信息（详见代码）。

对于排名查询操作，这个系统良心地帮我们省去了（）

对于班级成绩查询操作，基本和查询操作相同。

一些重要的坑点：

• 洛谷上的输出样例少了一些换行，以 PDF 上的为准
• PDF 上的 Showing the ranklist hurts students' self-esteem. Don't do that. 一句中的单引号是中文的，需要修改
• 遇到除数为 $0$ 的情况，输出 -nan 而非 nan
• 班级查询中的 $\texttt{Overall}$ 后有冒号，而四科后是没有冒号的；$\texttt{Overall}$ 查询的分别是全部通过的，通过 $\ge 3,\ge 2,\ge 1$ 科的和全部挂科的。

还有一些坑点，详见代码：

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstdlib>
#include <iomanip>
#include <vector>
#include <unordered_map>

using namespace std;

const double eps = 1e-5;

struct Student {
    string sid; // student ID
    int cid;  // class ID
    string name;
    int score[5]; // Chinese, Math, English and Programming
    int total = 0;
} ;

vector<Student> s;
unordered_map<string, bool> sid;

void speedup() {
    ios::sync_with_stdio(0);
    cin.tie(0), cout.tie(0);
}


void print(int i) {
    cout << s[i].sid << " " << s[i].cid << " ";
    cout << s[i].name << " ";
    for (int j = 1; j <= 4; ++j) cout << s[i].score[j] << " ";
    cout << s[i].total << " " << fixed << setprecision(2) << s[i].total/4.0+eps << '\n';
}

void Main_Menu() { // Main Menu
    cout << "Welcome to Student Performance Management System (SPMS).\n";
    cout << '\n';
    cout << "1 - Add\n";
    cout << "2 - Remove\n";
    cout << "3 - Query\n";
    cout << "4 - Show ranking\n";
    cout << "5 - Show Statistics\n";   
    cout << "0 - Exit\n";
    cout << '\n';
}

void Add() {
    cout << "Please enter the SID, CID, name and four scores. Enter 0 to finish.\n";
    string ss;

    while (cin >> ss) {
        if (ss == "0") break;

        Student tmp;
        tmp.sid = ss;
        cin >> tmp.cid >> tmp.name;
        for (int i = 1; i <= 4; ++i) {
            cin >> tmp.score[i];
            tmp.total += tmp.score[i];
        }

        if (!sid[ss]) s.push_back(tmp), sid[ss] = 1;
        else cout << "Duplicated SID.\n";

        //for (int i = 0; i < s.size(); ++i) print(i);

        cout << "Please enter the SID, CID, name and four scores. Enter 0 to finish.\n";
    }
}

void Remove() {
    cout << "Please enter SID or name. Enter 0 to finish.\n";
    string ss;

    while (cin >> ss) {
        if (ss == "0") break;

        int cnt = 0;
        for (int i = 0; i < s.size(); ++i) {
            Student a = s[i];
            if (a.sid == ss || a.name == ss) {
                sid[a.sid] = 0;
                s.erase(s.begin()+i);
                cnt ++;
                i --;
            }
        }
        //for (int i = 0; i < s.size(); ++i) print(i);

        cout << cnt << " student(s) removed.\n";
        cout << "Please enter SID or name. Enter 0 to finish.\n";
    }
}

void Query() {
    cout << "Please enter SID or name. Enter 0 to finish.\n";
    string ss;

    while (cin >> ss) {
        if (ss == "0") break;

        for (int i = 0; i < s.size(); ++i) {
            if (s[i].sid == ss || s[i].name == ss) {
                int rank = 1;
                for (int j = 0; j < s.size(); ++j)
                    if (s[j].total > s[i].total) rank ++;
                cout << rank << " " << s[i].sid << " " << s[i].cid << " ";
                cout << s[i].name << " ";
                for (int j = 1; j <= 4; ++j) cout << s[i].score[j] << " ";
                cout << s[i].total << " " << fixed << setprecision(2) << s[i].total/4.0+eps << '\n';
            }
        }

        cout << "Please enter SID or name. Enter 0 to finish.\n";
    }
}

void Show_Ranklist() { 
    cout << "Showing the ranklist hurts students\' self-esteem. Don\'t do that.\n";
}

void Show_Statistics() {
    cout << "Please enter class ID, 0 for the whole statistics.\n";
    int cid;
    cin >> cid;

    int num = 0;
    int sum[5] = {}, pass[5] = {}, fail[5] = {}, total[5] = {};
    for (int i = 0; i < s.size(); ++i) {
        if (s[i].cid == cid || cid == 0) {
            int cnt = 0;
            for (int j = 1; j <= 4; ++j) {
                sum[j] += s[i].score[j];
                if (s[i].score[j] >= 60) pass[j] ++, cnt ++;
                else fail[j] ++;
            }
            num ++, total[cnt] ++;
        }
    }

    for (int i = 1; i <= 4; ++i) {
        if (i == 1) cout << "Chinese\n";
        else if (i == 2) cout << "Mathematics\n";
        else if (i == 3) cout << "English\n";
        else cout << "Programming\n";

        if (!num) cout << "Average Score: " << "-nan" << '\n';
        else cout << "Average Score: " << fixed << setprecision(2) << (double)sum[i]/num+eps << '\n';
        cout << "Number of passed students: " << pass[i] << '\n';
        cout << "Number of failed students: " << fail[i] << '\n';
        cout << '\n';
    }

    cout << "Overall:\n";
    cout << "Number of students who passed all subjects: " << total[4] << '\n';
    cout << "Number of students who passed 3 or more subjects: " << total[4]+total[3] << '\n';
    cout << "Number of students who passed 2 or more subjects: " << total[4]+total[3]+total[2] << '\n';
    cout << "Number of students who passed 1 or more subjects: " << total[4]+total[3]+total[2]+total[1] << '\n';
    cout << "Number of students who failed all subjects: " << total[0] << '\n';
    cout << '\n';
} 

int main() {
//  freopen("UVA12412.in", "r", stdin);
//  freopen("UVA12412.out", "w", stdout);

    speedup();

    int op;
    Main_Menu();

    while (cin >> op) {
        if (op == 0) break;
        else if (op == 1) Add();
        else if (op == 2) Remove();
        else if (op == 3) Query();
        else if (op == 4) Show_Ranklist();
        else Show_Statistics();

        Main_Menu();
    }

    return 0;
}

CF1280B Beingawesomeism

分类讨论即可。

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <queue>

using namespace std;

typedef pair<int, int> pii;

int t, n, m, ans;
char s[65][65];

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0), cout.tie(0);

    cin >> t;
    while (t -- ) {
        ans = 4;
        cin >> n >> m;
        for (int i = 1; i <= n; ++i) cin >> s[i]+1;

        bool isA = 0, allA = 1, pointA = 0;
        for (int i = 1; i <= n; ++i) {
            for (int j = 1; j <= m; ++j) {
                if (s[i][j] == 'A') {
                    isA = 1;
                    if ((i == 1 && j == 1) || (i == 1 && j == m) || 
                        (i == n && j == 1) || (i == n && j == m)) pointA = 1;
                }
                else allA = 0;
            }
        }
        if (!isA) cout << "MORTAL" << endl;
        else if (allA) cout << 0 << endl;
        else {
            bool colA;

            colA = 1;
            for (int i = 1; i <= n; ++i) if (s[i][1] == 'P') colA = 0;
            if (colA) {
                cout << 1 << endl;
                continue;
            }
            colA = 1;
            for (int i = 1; i <= n; ++i) if (s[i][m] == 'P') colA = 0;
            if (colA) {
                cout << 1 << endl;
                continue;
            }
            colA = 1;
            for (int j = 1; j <= m; ++j) if (s[1][j] == 'P') colA = 0;
            if (colA) {
                cout << 1 << endl;
                continue;
            }
            colA = 1;
            for (int j = 1; j <= m; ++j) if (s[n][j] == 'P') colA = 0;
            if (colA) {
                cout << 1 << endl;
                continue;
            }

            if (pointA) {cout << 2 << endl; continue;}

            for (int i = 1; i <= n; ++i) {
                colA = 1;
                for (int j = 1; j <= m; ++j) {
                    if (s[i][j] == 'P')
                        colA = 0;
                }
                if (colA) {
                    cout << 2 << endl;
                    break;
                }
            }
            if (colA) continue;
            for (int j = 1; j <= m; ++j) {
                colA = 1;
                for (int i = 1; i <= n; ++i) {
                    if (s[i][j] == 'P')
                        colA = 0;
                }
                if (colA) {
                    cout << 2 << endl;
                    break;
                }
            }
            if (colA) continue;

            colA = 0;
            for (int i = 1; i <= n; ++i) if (s[i][1] == 'A') colA = 1;
            if (colA) {
                cout << 3 << endl;
                continue;
            }
            colA = 0;
            for (int i = 1; i <= n; ++i) if (s[i][m] == 'A') colA = 1;
            if (colA) {
                cout << 3 << endl;
                continue;
            }
            colA = 0;
            for (int j = 1; j <= m; ++j) if (s[1][j] == 'A') colA = 1;
            if (colA) {
                cout << 3 << endl;
                continue;
            }
            colA = 0;
            for (int j = 1; j <= m; ++j) if (s[n][j] == 'A') colA = 1;
            if (colA) {
                cout << 3 << endl;
                continue;
            }

            cout << 4 << endl;
        }
    }

    system("pause");
    return 0;
}