JinLou-C++day04

#include <iostream>
using namespace std;
int main(){
//    while(condition){
//        循环体
//    }
    int i = 0;
    while (i < 5){
        cout<< "hello" <<endl;
        i++;
    }
    // 求解 1 ~100累加和
    int j = 1;
    int sum = 0;
    while (j <=100){
//        sum = sum + j;
        sum += j;
        cout<< j << " ";
        j++;
    }
    // 换行
    cout <<endl;
    cout<< "sum = " << sum << endl;
}

求奇数和

#include <iostream>
using namespace std;
int main(){
    // 求解 1 ~100奇数累加和
    int j = 1;
    int sum = 0;
    while (j <=100){
        sum += j;
        cout<< j << " ";
        j+=2;
    }
    // 换行
    cout <<endl;
    cout<< "sum = " << sum << endl;
}

break 和 cotinue

都是可以中断循环的

• break 跳出本层循环；
• continue跳出本次循环执行下一次循环;

do while循环

不常用
语法：

do{循环语句} while(循环条件)
与while的区别 ：do while循环会先执行一次循环， 再去判断循环条件

#include <iostream>
using namespace std;
int main(){
//    int i = 1;
//    while (i < 1){
//        cout<< "sum = "<< endl;
//    }
//    do{
//        cout<< "sum "<< endl;
//    }while (i < 1);
    // do while 求 1 ~ 100 之间的累加和
    int i = 0;
    int sum = 0;
    do{
        i += 1;
        sum += i;

    }while(i <= 99);
    cout << "sum = " << sum << endl;

}

#include <iostream>
using namespace std;
int main(){
    //案例描述：系统随机⽣成⼀个1到100之间的数字，玩家进⾏猜测，
    // 如果猜错，提⽰玩家数字过⼤或过 ⼩，如果猜对恭喜玩家胜利，并且退出游戏。
    int generate_number = 40;
    int guess_number;
    while (true){
        cout << "please input you guess_number "  << endl;
        cin >> guess_number;
        if (guess_number > generate_number){
            cout << "too large "  << endl;
        }else if (guess_number < generate_number){
            cout << "too small "  << endl;
        }else{
            cout << "very good "  << endl;
            break;
        }
    }
}

电脑生成随机数

int main(){
    srand((unsigned int )time(NULL));
    int i = 0;
    while (i < 100){
        // rand()%n  生成 [0, n) 之间的随机整数
        // rand()%n + m 生成 [m, m+n) 之间的随机整数
        int num = rand()%100 + 1;
        cout << "num ="<< num  << endl;
        if (num==101){
            cout << "++++++++++++++++++++++++++++++++++"<< num  << endl;
        }
        i++;
    }
}

#include <iostream>
#include <ctime>
using namespace std;
int main(){
    //随机种子
    srand((unsigned int )time(NULL));
    //案例描述：系统随机⽣成⼀个1到100之间的数字，玩家进⾏猜测，
    // 如果猜错，提⽰玩家数字过⼤或过 ⼩，如果猜对恭喜玩家胜利，并且退出游戏。
    int generate_number;
    int guess_number;
    // [40, 100]
//    generate_number = rand()%61 + 40;
    generate_number = rand()%100 + 1; //随机生成 1 ~100 之间的整数
//    cout << "generate_number = " << generate_number << endl;

    while (true){
        cout << "please input you guess_number "  << endl;
        cin >> guess_number;
        if (guess_number > generate_number){
            cout << "too large "  << endl;
        }else if (guess_number < generate_number){
            cout << "too small "  << endl;
        }else{
            cout << "very good "  << endl;
            break;
        }

}}

for 循环(最常用)

语法
// for 和 while 可以互相转化

    for (初始表达式; 条件表达式; 步进表达式) {
        循环体
    }

int main() {
    for (int i = 0; i < 5; i++) {
        cout << "++++++++++++++++++++++++++++++++++" << i << endl;
    }
    int sum = 0;
    // for 求 1 ~ 100 之间的累加和
    for (int i = 1; i <= 100; ++i) {
        sum += i;
    }
    cout << "sum = " << sum << endl;
}

将上面的break 和continue案例使用for改写