Khóa học C++ từ cơ bản đến nâng cao

#include <iostream>
#include <string>
#include <limits> // Can thiet de su dung numeric_limits

int main() {
    string word, line;

    cout << "Nhap mot tu (vd: XinChao): ";
    cin >> word; // Chi doc den khoang trang dau tien
    cout << "Ban vua nhap tu: " << word << endl;

    // Can xoa bo dem ban phim sau khi dung cin >>
    // Neu khong, ky tu xuong dong con lai se bi getline doc ngay lap tuc
    cin.ignore(numeric_limits<streamsize>::max(), '\n');

    cout << "Nhap mot dong (vd: Xin chao the gioi): ";
    getline(cin, line); // Doc ca dong, bao gom ca khoang trang
    cout << "Ban vua nhap dong: " << line << endl;

    return 0;
}

#include <iostream>
#include <string>

int main() {
    string example = "Lap trinh C++";

    // Lay do dai
    cout << "Chuoi: '" << example << "'" << endl;
    cout << "Do dai chuoi: " << example.length() << endl; // Hoac example.size()

    // Truy cap ky tu
    cout << "Ky tu dau tien: " << example[0] << endl; // Cach thong thuong
    cout << "Ky tu tai vi tri 4: " << example.at(4) << endl; // An toan hon

    // In tung ky tu mot
    cout << "Cac ky tu: ";
    for (int i = 0; i < example.length(); ++i) {
        cout << example[i] << " ";
    }
    cout << endl;

    return 0;
}

#include <iostream>
#include <string>

int main() {
    string part1 = "Xin chao";
    string part2 = " the gioi!";

    // Noi chuoi bang toan tu +
    string fullString = part1 + part2;
    cout << "Noi bang +: " << fullString << endl; // Tao ra chuoi moi

    // Noi chuoi bang append()
    string message = "Hom nay la ";
    message.append("thu Hai."); // Noi vao chuoi hien co
    cout << "Noi bang append(): " << message << endl;

    // Noi ky tu vao cuoi chuoi
    message += '!'; // Tuong duong voi message.push_back('!');
    cout << "Noi ky tu: " << message << endl;


    return 0;
}

#include <iostream>
#include <string>

int main() {
    string sentence = "Hoc lap trinh C++ that la thu vi.";
    string wordToFind = "C++";
    string nonExistentWord = "Java";

    // Tim kiem tu "C++"
    size_t pos = sentence.find(wordToFind);

    if (pos != string::npos) { // Kiem tra xem co tim thay khong
        cout << "Tim thay '" << wordToFind << "' tai vi tri: " << pos << endl;
        // Vi tri nay la index bat dau cua chuoi con tim thay
    } else {
        cout << "Khong tim thay '" << wordToFind << "' trong chuoi." << endl;
    }

    // Tim kiem tu "Java"
    pos = sentence.find(nonExistentWord);
    if (pos != string::npos) {
         cout << "Tim thay '" << nonExistentWord << "' tai vi tri: " << pos << endl;
    } else {
        cout << "Khong tim thay '" << nonExistentWord << "' trong chuoi." << endl;
    }

    // Tim ky tu
    size_t charPos = sentence.find('t');
     if (charPos != string::npos) {
         cout << "Ky tu 't' dau tien tai vi tri: " << charPos << endl;
    }


    return 0;
}

#include <iostream>
#include <string>

int main() {
    string data = "ID:12345-STATUS:Active-USER:Admin";

    // Lay ID (tu vi tri 3, do dai 5 ky tu)
    string id = data.substr(3, 5);
    cout << "ID: " << id << endl; // Output: 12345

    // Lay STATUS (tim vi tri "STATUS:", sau do lay tiep)
    size_t statusPos = data.find("STATUS:");
    if (statusPos != string::npos) {
        string status = data.substr(statusPos + 7, 6); // +7 de bo qua "STATUS:"
        cout << "STATUS: " << status << endl; // Output: Active
    }

    // Lay USER (tim vi tri "USER:", sau do lay den het)
     size_t userPos = data.find("USER:");
    if (userPos != string::npos) {
        string user = data.substr(userPos + 5); // +5 de bo qua "USER:", lay den het
        cout << "USER: " << user << endl; // Output: Admin
    }

    return 0;
}

#include <iostream>
#include <string>

int main() {
    string sentence = "Ban nen hoc Java de co viec lam.";

    // Tim vi tri cua "Java"
    size_t pos = sentence.find("Java");

    if (pos != string::npos) {
        // Thay the "Java" (4 ky tu) bang "C++" (3 ky tu) tai vi tri tim thay
        sentence.replace(pos, 4, "C++");
        cout << "Sau khi thay the: " << sentence << endl;
        // Output: Ban nen hoc C++ de co viec lam.
    } else {
        cout << "Khong tim thay tu can thay the." << endl;
    }

    return 0;
}

#include <iostream>
#include <string>

int main() {
    string baseString = "Day la chuoi goc.";

    // Chen chuoi vao giua
    baseString.insert(7, "mot "); // Chen "mot " vao vi tri 7
    cout << "Sau khi chen: " << baseString << endl;
    // Output: Day la mot chuoi goc.

    // Xoa mot phan
    baseString.erase(4, 3); // Xoa 3 ky tu " la" tai vi tri 4
    cout << "Sau khi xoa: " << baseString << endl;
    // Output: Day mot chuoi goc.

    // Xoa den het tu mot vi tri
    baseString.erase(4); // Xoa tu vi tri 4 den het
    cout << "Sau khi xoa tu vi tri 4 den het: " << baseString << endl;
    // Output: Day

    return 0;
}

#include <iostream>
#include <string>
#include <limits> // Can thiet cho numeric_limits

int main() {
    string str1 = ""; // Chuoi rong
    string str2 = "Hello"; // Chuoi khong rong
    string userInput;

    if (str1.empty()) {
        cout << "str1 la chuoi rong." << endl;
    } else {
        cout << "str1 khong rong." << endl;
    }

     if (str2.empty()) {
        cout << "str2 la chuoi rong." << endl;
    } else {
        cout << "str2 khong rong." << endl;
    }

    cout << "Nhap gi do (hoac enter ngay de bo trong): ";
    getline(cin, userInput);

    if (userInput.empty()) {
        cout << "Ban da nhap mot dong rong." << endl;
    } else {
        cout << "Ban da nhap dong: '" << userInput << "'" << endl;
    }

    return 0;
}

#include <iostream>
#include <string> // Can thiet cho stoi, stod, to_string
#include <limits> // Can thiet cho numeric_limits (neu can xu ly input)
#include <stdexcept> // Can thiet de bat exception cho stoi, stod

int main() {
    string strNum = "123";
    string strDouble = "3.14159";
    string invalidStr = "abc";
    int age = 25;
    double price = 99.99;

    // Chuyen tu chuoi sang so
    try { // Nen dung try-catch vi cac ham stoi/stod co the gay loi
        int num = stoi(strNum);
        double dbl = stod(strDouble);
        // int errorNum = stoi(invalidStr); // Dong nay se gay ra exception

        cout << "Chuoi '" << strNum << "' thanh so nguyen: " << num << endl;
        cout << "Chuoi '" << strDouble << "' thanh so thuc: " << dbl << endl;

    } catch (const invalid_argument& ia) {
        cerr << "Loi doi so khong hop le khi chuyen doi: " << ia.what() << '\n';
    } catch (const out_of_range& oor) {
        cerr << "Loi ngoai pham vi khi chuyen doi: " << oor.what() << '\n';
    }


    // Chuyen tu so sang chuoi
    string ageStr = to_string(age);
    string priceStr = to_string(price);

    cout << "So nguyen " << age << " thanh chuoi: '" << ageStr << "'" << endl;
    cout << "So thuc " << price << " thanh chuoi: '" << priceStr << "'" << endl;

    // Ket hop so (da thanh chuoi) voi chuoi khac
    cout << "Toi " + ageStr + " tuoi." << endl;


    return 0;
}