C#语言基础

lesson#3 循环+一维数组

内容：

1. 循环-for, while, do while；

2. 逻辑运算符；

1. While 循环；

 //循环变量初始化

            int count = 1;

 //循环条件

            while (count <= 5)

 //循环体

            {

                Console.WriteLine("Hello World");

 //循环变量增加

                count = count + 1;

            }

            Console.WriteLine("zhangsan");

 //练习1：

// 编写程序实现功能，计算 100 至 10000 之间有多少个数其各位数字之和是 7.（例如 241 2+4+1=7)

            Console.WriteLine("请输入一个100-10000之间的数");

            int i = 100, t = 0;

            while (i < 10000)

            {

                if (i / 1000 + i % 1000 / 100 + i % 100 / 10 + i % 10 == 7)

                {

                    t++;

                    Console.WriteLine(i);

                }

                i++;

            }

            Console.WriteLine(t);

//练习2：

//打印 1+2+3+…+100 的值

            int i = 0;

            int sum = 0;

            while (i < 100)

            {

                i++;//1,2

                sum = sum + i;//0+1+2

            }

            Console.WriteLine(sum);

2. break和continue；

//break在switch语句里面跳出开头，在循环结构里面跳出循环体

            int i = 0;

            while (true)

            //while (i < 5)

            {

                if (i == 3)

                {

                    break;

                }

                Console.WriteLine(i);

                i++;

            }

---------------------------------------------------------

            while (true)

            {

                Console.WriteLine("请输入一个数字：");

                double i = Convert.ToDouble(Console.ReadLine());

                if (i < 0)

                {

                    break;

                }

            }

            Console.WriteLine("您输入的数字不能小于0");

 //continue表示提前结束本次循环，进入到下一次循环

            int i = 0;

            while (i < 100)

            {

                i++;

                if (i % 2 == 1)

                {

                    continue;

                }

                Console.WriteLine(i);

            }

3. do..while循环；

   int i = -10;

            //while (i>0)

            //{

            //    Console.WriteLine("Hello World");

            //}

            do

            {

                Console.WriteLine("Hello World");

            } while (i > 10);

            int N = 0, sum = 0;

            while (sum < 10000)

            {

                N++;

                sum = sum + N;

            }

            Console.WriteLine(sum - N);

            Console.WriteLine(N - 1);

4. for循环；

int i = 0;

            while (i < 100)

            {

                i++;

                Console.WriteLine(i);

                //for循环用在已知循环次数的情况

            }

            for (int j = 0; j < 100; j++)

            {

                Console.WriteLine(j);

            }

 //练习题1

            Console.WriteLine("请输入一个100-10000之间的数");

            int t = 0;

            for (int i = 100; i < 10000; i++)

            {

                if (i / 1000 + i % 1000 / 100 + i % 100 / 10 + i % 10 == 7)

                {

                    t++;

                    Console.WriteLine(i);

                }

            }

            Console.WriteLine(t);

// 练习题2

//打印 1-100 中不能被 7 整除又不包含 7 的数

            for (int i = 0; i < 101; i++)

            {

                if (i % 7 != 0 && i % 10 / 10 != 7 && i % 10 != 7)

                {

                    Console.WriteLine(i)