while循环

while (i<10) {
    Console.WriteLine(i);// 1 2 3 4 5 6 7 8 9
    i++;
}

输入整数n，求1+2+3+...+n的和

int n = Convert.ToInt32(Console.ReadLine());
int sum = 0;
while (n > 0) {
    sum += n--;
}
Console.WriteLine(sum);

输出1-100之间的偶数

int i = 1;
while (i <= 100) {
    if (i % 2 == 0) {
        Console.WriteLine(i);
    }
    i++;
}

3n+1问题

int n = Convert.ToInt32(Console.ReadLine());
int i = 0;
while (n != 1) {
    if (n % 2 == 0)
    {
        n = n / 2;
    }
    else { 
        n = 3 * n +1;
    }
    i++;
}
Console.WriteLine(i);

保留两位小数

double num = 1.23234;
// 1.23  保留两位小数
Console.WriteLine(num.ToString("0.00"));

输入n个学生的年龄，求出平均年龄

int n= Convert.ToInt32(Console.ReadLine());
int t = n;
double ageSum = 0;
while (n > 0) {
    ageSum += Convert.ToInt32(Console.ReadLine());
    n--;            
}
Console.WriteLine("平均年龄为：{0}",(ageSum  / t).ToString("0.00"));

for循环

for (int i = 1; i < 10; i++) { 
    Console.WriteLine(i);// 1 2 3 4 5 6 7 8 9 
}

输入n，m，计算n-m之间(包含)能被17整除的数字的和

int n = Convert.ToInt32(Console.ReadLine());
int m = Convert.ToInt32(Console.ReadLine());
int max,min;
if (n > m)
{
    max = n;
    min = m;
}
else {
    max = m;
    min = n;
}
int sum = 0;
for (; min <= max; min++) {
    if (min % 17 ==0) {
        sum += min;
    }
}
Console.WriteLine(sum);

do while循环

int i =0;
do {
    Console.WriteLine(i);// 1 2 3 4 5 6 7 8 9
    i++;
} while (i < 10);

输入整数a,n，计算a的n次方

int a = Convert.ToInt32(Console.ReadLine());
int n = Convert.ToInt32(Console.ReadLine());
int multiply = 1;
for (int i=1;i<=n;i++) {
    multiply *= a;
}
Console.WriteLine(multiply);