在C++中，可以使用if-else語句、switch語句或者三元運算符（條件運算符）來實現條件判斷。下面是這三種方法的示例：

1. if-else語句：

#include <iostream>
using namespace std;

int main() {
    int number = 10;

    if (number > 0) {
        cout << "The number is positive." << endl;
    } else if (number < 0) {
        cout << "The number is negative." << endl;
    } else {
        cout << "The number is zero." << endl;
    }

    return 0;
}

2. switch語句：

#include <iostream>
using namespace std;

int main() {
    int day = 3;

    switch (day) {
        case 1:
            cout << "Monday" << endl;
            break;
        case 2:
            cout << "Tuesday" << endl;
            break;
        case 3:
            cout << "Wednesday" << endl;
            break;
        case 4:
            cout << "Thursday" << endl;
            break;
        case 5:
            cout << "Friday" << endl;
            break;
        case 6:
            cout << "Saturday" << endl;
            break;
        case 7:
            cout << "Sunday" << endl;
            break;
        default:
            cout << "Invalid day" << endl;
    }

    return 0;
}

3. 三元運算符（條件運算符）：

#include <iostream>
using namespace std;

int main() {
    int number = 10;

    string result = (number > 0) ? "The number is positive." : (number < 0) ? "The number is negative." : "The number is zero.";

    cout << result << endl;

    return 0;
}

以上三種方法都可以實現條件判斷，根據具體需求和場景選擇合適的方法。