C++选择结构

#include <iostream>
 
using namespace std;
 
 
int main() {
    int num1 = 10;
    int num2 = 20;
//    单行条件
    if (num1 < num2) {
        cout << "num1 小于 num2" << endl;
    }
//    多行条件
    if (num1 > num2) {
        cout << "num1 大于 num2" << endl;
 
    } else {
        cout << "num1 小于 num2" << endl;
    }
//多条件语句
    int num3;
    cout << "请输入一个数字：" << endl;
    cin >> num3;
    if (num3 > 10) {
        cout << "num3 大于 10" << endl;
    } else if (num3 > 9) {
        cout << "num3 大于 9" << endl;
    } else if (num3 > 8) {
        cout << "num3 大于 8" << endl;
    } else if (num3 > 7) {
        cout << "num3 大于 7" << endl;
    } else {
        cout << "num3 小于等于 7" << endl;
    }
//    嵌套if
    int num4 = 10;
    int num5 = 20;
    if (num4 == 10) {
        cout<<"num4 等于10"<<endl;
        if(num5==20){
            cout<<"num4 等于10 num5 等于20"<<endl;
        }else{
            cout<<"num4 等于10 num5 不等于20"<<endl;
        }
    } else {
        cout<<"num4 不等于10"<<endl;
    }
    return 0;
}

#include <iostream>
 
using namespace std;
 
 
int main() {
    int a = 10;
    int b = 20;
//    三目运算返回值
    int c = a > b ? a : b;
    cout << "c=" << c << "\n";
//    三目运算返回变量
    (a > b ? a : b) = 1000;
    cout << a << endl;
    cout << b << endl;
 
    return 0;
}

#include <iostream>
 
using namespace std;
 
 
int main() {
//switch
    cout << "请输入你的成绩：" << endl;
    int score = 0;
    cin >> score;
    switch (score) {
        case 10:
            cout << "很优秀10" << endl;
            break;
        case 9:
            cout << "很优秀9" << endl;
            break;
        case 8:
            cout << "很优秀8" << endl;
            break;
        case 7:
            cout << "很优秀7" << endl;
            break;
        default:
            cout << "^_^" << endl;
            break;
    }
 
    return 0;
}

#include <iostream>
#include <string>
 
 
using namespace std;
 
int main() {
    int select = 2;
    switch (select) {
        case 1:
            cout << "1" << endl;
            break;
        case 2: {
            cout << "1" << endl;
            cout << "1" << endl;
            cout << "1" << endl;
            cout << "1" << endl;
        }
            break;
        default:
            break;
    }
    return 0;
}