刷题笔记 - December 2023

1.DFS_example

#include <iostream>
#include <vector>
#include <queue>

using namespace std;

vector<vector<int>> arrayList = {
    {1, 2}, {0, 3, 4}, {0, 5}, {1}, {1}, {2}
};

void dfs(int node, vector<bool>& visited) {
    visited[node] = true;
    cout << node << " ";

    for (int neighbor : arrayList[node]) {
        if (!visited[neighbor]) {
            dfs(neighbor, visited);
        }
    }
}

void bfs(int startNode, vector<bool>& visited) {
    queue<int> q;
    q.push(startNode);
    visited[startNode] = true;

    while (!q.empty()) {
        int currentNode = q.front();
        cout << currentNode << " ";
        q.pop();

        for (int neighbor : arrayList[currentNode]) {
            if (!visited[neighbor]) {
                q.push(neighbor);
                visited[neighbor] = true;
            }
        }
    }
}

int main() {
    int nodes = 6;
    vector<bool> visited1(nodes, false);
    cout << endl << "DFS: ";    dfs(0, visited1);
    vector<bool> visited2(nodes, false);
    cout << endl << "BFS: ";    bfs(0, visited2);

    return 0;
}

2.2023，知识点：搜索

#include <iostream>

using namespace std;

bool exist2023(int x) {
    int x2[4] = {3, 2, 0, 2};
    int index = 0;
    while(x) {
        int temp = x % 10;
        if(temp == x2[index]) {
            index++;
            if(index == 4) {
                return true;
            }
        }
        x = (x - temp) / 10;
    }
    return false;
}

int main() {
    int count = 0;
    for (int x = 12345678; x <= 98765432; x++) {
        if (exist2023(x)) {
            count++;
        }
    }
    cout << 98765432 - 12345678 + 1 - count << endl;
    return 0;
}

3.硬币兑换，知识点：数学，枚举

#include <iostream>
#include <vector>

using namespace std;

int main() {
    int n;
    cin >> n;
//  注：兑换的两新硬币面值不能一样，且只统计旧硬币，巨坑
    vector<int> map(2 * n + 1, 0);
    int result = 0;
    for (int i = 1; i <= n; i++) {
        for (int j = i + 1; j <= n; j++) {
            map[i + j] += i;
            if(map[i + j] > result) {
                result = map[i + j];
            }
        }
    }
//    for(int i = 1; i < 2 * n + 1; i++) {
//      cout << "map[" << i << "] = " << map[i] << endl;
//  }
    cout << result;
    return 0;
}

4.工作时长，知识点：字符串

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#include <iostream>
#include <fstream>

using namespace std;

string deleteZero(string s) {
    if(s.size() == 2 && s[0] == '0') {
        s.erase(0, 1);
    }
    return s;
}

int calculateTime(int h, int m, int s, int h2, int m2, int s2) {
    int time = 0;
    if(s2 < s) {
        m2--;
        if(m2 < m) {
            return 3600 * (h2 - 1 - h) + 60 * (m2 + 60 - m) + (s2 + 60 - s);
        } else {
            return 3600 * (h2 - h) + 60 * (m2 - m) + (s2 + 60 - s);
        }
    } else {
        if(m2 < m) {
            return 3600 * (h2 - 1 - h) + 60 * (m2 + 60 - m) + (s2 - s);
        } else {
            return 3600 * (h2 - h) + 60 * (m2 - m) + (s2 - s);
        }
    }
}

int main() {
    // work.txt为excel日期排序的文本，自定义格式hh:mm:ss
    ifstream file("work.txt");
    string line, line2, S;
    int h, h2, s, m, m2, s2;
    int totalTime = 0;
    while(getline(file, line) && getline(file, line2)) {
        S = line.substr(0, 2);  h = stoi(deleteZero(S));
        S = line.substr(3, 2);  m = stoi(deleteZero(S));
        S = line.substr(6, 2);  s = stoi(deleteZero(S));
        S = line2.substr(0, 2); h2 = stoi(deleteZero(S));
        S = line2.substr(3, 2); m2 = stoi(deleteZero(S));
        S = line2.substr(6, 2); s2 = stoi(deleteZero(S));
        cout << h << "\t" << m << "\t" << s << "\t" << h2 << "\t" << m2 << "\t" << s2;
        cout << "\t" << "time:" << "\t" << calculateTime(h, m, s, h2, m2, s2) << endl;
        totalTime += calculateTime(h, m, s, h2, m2, s2);
    }
    cout << totalTime;// 5101913
    file.close();
    return 0;
}

5.求和，知识点：数学

#include <iostream>

using namespace std;

int main() {
    cout << (1LL + 20230408LL) * 20230408LL / 2 << endl;
    return 0;
}

6.日期统计，知识点：枚举，字符串

#include <iostream>
#include <vector>

using namespace std;

int main() {
    vector<int> Array(100, 0);
    int count = 0;
    for(int i = 0; i < 100; i++) {
        cin >> Array[i];
    }
    int day[12] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
    int temp[8] = {2, 0, 2, 3};
    // 枚举每一个月
    for(int i = 1; i <= 12; i++) {
        cout << "\nmonth:" << i << "\nday:";
        if(i <= 9) {
            temp[4] = 0;
            temp[5] = i; 
        } else {
            temp[4] = i / 10;
            temp[5] = i % 10;               
        }
        // 枚举每一天
        for(int j = 1; j <= day[i - 1]; j++) {
            cout << j << " ";
            if(j <= 9) {
                temp[6] = 0;
                temp[7] = j; 
            } else {
                temp[6] = j / 10;
                temp[7] = j % 10;               
            }
            // 暴力对比序列
            int index = 0;
            for(int k = 0; k < 100; k++) {
                if(Array[k] == temp[index]) {
                    index++;
                }
                if(index == 8) {
                    count++;
                    goto end_loop;
                }
            }
            end_loop: continue;
        }
    }
    cout << endl << count;
    return 0;
}

7.幸运数，知识点：枚举，数学

#include <iostream>
#include <vector>

using namespace std;

int main() {
    int count = 0;
    for(int i = 10; i <= 99; i++) {
        if(i % 10 == i / 10) {
//          cout << i << endl;
            count++;
        }
    }
    for(int i = 1000; i <= 9999; i++) {
        int x1 = i / 1000;
        int x2 = i % 1000 / 100;
        int y1 = i % 100 / 10;
        int y2 = i % 10;
        if(x1 + x2 == y1 + y2) {
//          cout << i << endl;
            count++;
        }
    }
    for(int i = 100000; i <= 999999; i++) {
        int x1 = i / 100000;
        int x2 = i % 100000 / 10000;
        int x3 = i % 10000 / 1000;
        int y1 = i % 1000 / 100;
        int y2 = i % 100 / 10;
        int y3 = i % 10;
        if(x1 + x2 + x3 == y1 + y2 + y3) {
//          cout << i << endl;
            count++;
        }
    }
    for(int i = 10000000; i <= 99999999; i++) {
        int x1 = i / 10000000;
        int x2 = i % 10000000 / 1000000;
        int x3 = i % 1000000 / 100000;
        int x4 = i % 100000 / 10000;
        int y1 = i % 10000 / 1000;
        int y2 = i % 1000 / 100;
        int y3 = i % 100 / 10;
        int y4 = i % 10;
        if(x1 + x2 + x3 + x4 == y1 + y2 + y3 + y4) {
//          cout << i << endl;
            count++;
        }
    }
    cout << count;
    return 0;
}

8.三元组中心问题，知识点：枚举

#include <iostream>
#include <vector>

using namespace std;

int main() {
    int n;
    cin >> n;
    vector<int> Array(n, 0);
    vector<int> flag(n, 0);
    for(int i = 0; i < n; i++) {
        cin >> Array[i];
    }
    for(int i = 0; i < n - 2; i++) {
        for(int j = i + 1; j < n - 1; j++) {
            for(int k = j + 1; k < n; k++) {
                if(Array[i] < Array[j] && Array[j] < Array[k]) {
//                  cout << Array[i] << " " << Array[j] << " " << Array[k] << endl;
                    flag[j] = 1;
                }
            }
        }
    }
    int count = 0;
    for(int i = 0; i < n; i++) {
        if(flag[i] == 1) {
            count++;
        }
    }
    cout << count << endl;
    return 0;
}

9.等腰三角形，知识点：模拟，字符串

#include <iostream>
#include <vector>
#include <sstream>

using namespace std;

int main() {
    int n;
    cin >> n;
    // 生成递增字符
    string s;
    ostringstream S;
    for(int i = 1; i <= 4 * (n - 1); i++) {
        S << i;
    }
    s = S.str();
    // 初始化三角形
    vector<vector<char>> Array(n, vector<char>(2 * n - 1, 0));
    for(int i = 0; i < n - 1; i++) {
        for(int j = 0; j < n + i - 1; j++) {
            Array[i][j] = '.';
        }
    }
    int index = 0;
    // 填充左边
    for(int i = 0; i < n - 1; i++) {
        Array[i][n - i - 1] = s[index++];
    }
    // 填充底边
    for(int i = 0; i < 2 * n - 1; i++) {
        Array[n - 1][i] = s[index++];
    }
    // 填充右边
    for(int i = n - 2; i > 0; i--) {
        Array[i][n + i - 1] = s[index++];
    }
    for(int i = 0; i < n; i++) {
        for(int j = 0; j < n + i; j++) {
            cout << Array[i][j];
        }
        cout << endl;
    }
    return 0;
}

12.人物相关性分析，知识点：字符串，模拟

#include <iostream>

using namespace std;

int main() {
    int K;
    string s;
    cin >> K;
    cin.ignore();
    getline(cin, s);
    // 标记两个人物的下标
    int index = -1, index2 = -1, count = 0;
    for(int i = 0; i < s.size(); i++) {
        if(s.substr(i, 5) == "Alice") {
            index = i;
            if(index2 > -1 && index - index2 - 3 <= K) {
                count++;
            }
        }
        if(s.substr(i, 3) == "Bob") {
            index2 = i;
            if(index > -1 && index2 - index - 5 <= K) {
                count++;
            }
        }
    }
    cout << count;
    return 0;
}

13.子串分值，知识点：字符串，枚举

#include <iostream>

using namespace std;

int f(string s) {
    int map[26] = {0};
    for(char c : s) {
        map[c - 'a']++;
    }
    int count = 0;
    for(int i : map) {
        if(i == 1) {
            count++;
        }
    }
    return count;
}

int main() {
    string s;
    getline(cin, s);
    int total = 0;
    // 遍历所有子串
    for (int i = 0; i < s.size(); i++) {
        for (int j = 1; j <= s.size() - i; j++) {
            cout << s.substr(i, j) << "\tf = " << f(s.substr(i, j)) << endl;
            total += f(s.substr(i, j));
        }
    }
    cout << total;
    return 0;
}

14.音节判断，知识点：模拟，字符串

#include <iostream>

using namespace std;

int main() {
    string s;
    cin >> s;
    int flag = 1, count = 0;
    for (int i = 0; i < s.length(); i++) {
        if (flag == 1 && s[i] != 'a' && s[i] != 'e' && s[i] != 'i' && s[i] != 'o' && s[i] != 'u') {
            count++;
            flag = 0;
        } else if (flag == 0 && (s[i] == 'a' || s[i] == 'e' || s[i] == 'i' || s[i] == 'o' || s[i] == 'u')) {
            count++;
            flag = 1;
        }
    }
    if (count == 4) {
        cout << "yes";
    } else {
        cout << "no";
    }
    return 0;
}

15.外卖店优先级，知识点：模拟，数据结构

#include <iostream>
#include <vector>

using namespace std;

int main() {
    int N, M, T;
    cin >> N >> M >> T;
    // N个商家, T天订单，优先缓存
    vector<vector<int>> order(N, vector<int> (T + 1, 0));
    vector<int> prior(N, 0);
    int ts, id;
    for(int i = 0; i < M; i++) {
        cin >> ts >> id;
        if(ts <= T) {
            order[id - 1][ts - 1]++;
        }
    }
    for(int i = 0; i < T; i++) {
        for(int j = 0; j < N; j++) {
            if(order[j][i] > 0) {
                order[j][T] += order[j][i] * 2;
            } else {
                order[j][T] = max(0, order[j][T] - 1);
            }
            if(order[j][T] > 5) {
                prior[j] = 1;
            } else if (order[j][T] <= 3) {
                prior[j] = 0;
            }
        }
    }
//  for(int i = 0; i < N; i++) {
//      for(int j = 0; j < T + 1; j++) {
//          cout << order[i][j] << " ";
//      }
//      if(prior[i]) {
//          cout << "\tyes";
//      } else {
//          cout << "\tno";
//      }
//      cout << endl;
//  }
    int count = 0;
    for(int i = 0; i < N; i++) {
        if(prior[i] == 1) {
            count++;
        }
    }
    cout << count;
    return 0;
}

16.特别数的和，知识点：模拟，数学

#include <iostream>

using namespace std;

bool goodNumber(int x) {
    int y;
    while(x) {
        y = x % 10;
        if(y == 2 || y == 0 || y == 1 || y == 9) {
            return true;
        }
        x = (x - y) / 10;
    }
    return false;
}

int main() {
    int n, result = 0;
    cin >> n;
    for(int i = 1; i <= n; i++) {
        if(goodNumber(i)) {
//          cout << i << " ";
            result += i;
        }
    }
    cout << result;
    return 0;
}

17.清理水域，知识点：模拟，数据结构

#include <iostream>
#include <vector>

using namespace std;

int main() {
    int n, m, t;
    int r1, c1, r2, c2;
    cin >> n >> m >> t;
    vector<vector<int>> water(n, vector<int> (m, 0));
    for(int i = 0; i < t; i++) {
        cin >> r1 >> c1 >> r2 >> c2;
        for(int j = r1 - 1; j < r2; j++) {
            for(int k = c1 - 1; k < c2; k++) {
                water[j][k] = 1;
            }
        }
    }
    int count = 0;
    for(int i = 0; i < n; i++) {
        for(int j = 0; j < m; j++) {
            if(water[i][j] == 1) {
                count++;
            }
//          cout << water[i][j] << " ";
        }
//      cout << endl;
    }
    cout << n * m - count;
    return 0;
}

19.大乘积，知识点：排序，枚举

#include <iostream>
#include <algorithm>

using namespace std;

bool smaller(int x, int y) {
    return x > y;
}

int main() {
    int count = 0;
    int number[30] = {
        99, 22, 51, 63, 72, 61, 20, 88, 40, 21,
        63, 30, 11, 18, 99, 12, 93, 16, 7, 53,
        64, 9, 28, 84, 34, 96, 52, 82, 51, 77
    };
    sort(number, number + 30, smaller);
    for(int i = 0; i < 29; i++) {
        if(number[i] * number[i + 1] < 2022) {
            break;
        }
        for(int j = i + 1; j < 30; j++) {
            if(number[i] * number[j] < 2022) {
                break;
            } else {
//              cout << number[i] << " * " << number[j] << " = " << number[i] * number[j] << endl;
                count++;
            }
        }
    }
    cout << count;
    return 0;
}

20.龙虎斗，知识点：模拟，数学

#include <iostream>
#include <vector>

using namespace std;

int n, m, p1, p2, s1, s2;

// 计算龙虎势力差
int HP(vector<int> game, int p2) {
    game[p2 - 1] += s2;
    int dragon = 0, tiger = 0;
    for(int i = 0; i < m - 1; i++) {
        dragon += game[i] * (m - 1 - i);
    }
    for(int i = n - 1; i >= m; i--) {
        tiger += game[i] * (i - m + 1);
    }
    return abs(dragon - tiger);
}

int main() {
    cin >> n;
    vector<int> game(n, 0);
    for(int i = 0; i < n; i++) {
        cin >> game[i];
    }
    cin >> m >> p1 >> s1 >> s2;
    game[p1 - 1] += s1;
    // 计算空投兵营
    int minHP = 9999;
    for(int i = 1; i <= n; i++) {
        if(HP(game, i) < minHP) {
            minHP = HP(game, i);
            p2 = i;
        }
    }
    cout << p2;
    return 0;
}