C#基础 第三天

#region 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!");
            //    //循环变量增量
            //    count++;

            //}

            //int count = 100;
            //int sum = 0;
            //while (count<=10000)
            //{
            //    if (7==count % 10 + count % 100 / 10 + count % 1000 / 100 + count / 1000)
            //    {
            //        sum += 1;
            //    }
            //    count++;
            //}
            //Console.WriteLine(sum);

            //int num = 1;
            //while (num<=100)
            //{
            //    if (num%2==0)
            //    {
            //        Console.Write(num+",");
            //    }
            //    num++;
            //}
            //Console.WriteLine();

            //int num1 = 1;
            //int sum1 = 0;
            //while (num1<=100)
            //{
            //    sum1 += num1;
            //    num1++;
            //}
            //Console.WriteLine(sum1);
            #endregion

            #region break和continue
            //break在switch语句里面跳出开头，在循环结构里面挑出循环体
            //int i = 0;
            //while (i<5)
            //{
            //    if (i==3)
            //    {
            //        break;
            //    }
            //    Console.WriteLine(i);
            //    i++;
            //}

            //键盘输入数字，如果输入小于0，跳出循环
            //while (true)
            //{
            //    Console.WriteLine("请输入数字：");
            //    double a = double.Parse(Console.ReadLine());
            //    if (a<0)
            //    {
            //        break;
            //    }
            //}

            //Console.WriteLine("输入错误！");

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

            #region do ....while循环
            //int i = -10;
            //while (i>0)
            //{
            //    Console.WriteLine("hello world");
            //}

            //int i = -10;
            //do
            //{
            //    Console.WriteLine("hello world");
            //}
            //while (i>0);
            //求sum=1+2+3+…+N;求sum不超过10000的最大整数值和项值N。
            //int N =0;
            //int sum = 0;
            //while (sum < 10000)
            //{
            //    N++;
            //    Console.WriteLine(N);
            //    sum += N;
            //    Console.WriteLine(sum);
            //}
            //Console.WriteLine("最大整数项：{0}，项值：{1}", sum - N, N - 1);

            #endregion

            #region for循环
            //for循环用在已知循环次数的情况
            //int sum = 0;
            //for (int i = 0; i < 100; i++)
            //{
            //    sum += i;
            //    Console.WriteLine(sum);
            //}
            //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)
            //int sum = 0;
            //for (int i = 100; i < 10000; i++)
            //{
            //    if (i/1000+i%1000/100+i%100/10+i%10==7)
            //    {
            //        Console.WriteLine(i);
            //        sum++;
            //    }
            //}
            //Console.WriteLine(sum);
            //2.打印出1-100之间所有的偶数
            //for (int i = 0; i <= 100; i++)
            //{
            //    if (i%2==0)
            //    {
            //        Console.WriteLine(i);
            //    }
            //}
            //3.打印1+2+3+…+100的值
            //int sum1 = 0;
            //for (int i = 0; i <= 100; i++)
            //{
            //    sum1 += i;

            //}
            //Console.WriteLine(sum1);

            //for (int i = 0; i <= 100; i++)
            //{
            //    if (i%7!=0&&i%10!=7&&i/10!=7)
            //    {
            //        Console.WriteLine(i);
            //    }
            //}

            //第一种方法
            //int sum = 0;
            //for (int j = 0; j < 100; j++)
            //{
            //    if (j%2==0)
            //    {
            //        continue;
            //    }
            //    sum += j;
            //}
            //Console.WriteLine(sum);
            //第二种方法
            //int sum = 0;
            //for (int i = 0; i < 100; i=i+2)
            //{
            //    sum += i;
            //}
            //Console.WriteLine(sum);
            #endregion

            #region 循环嵌套
            //外层循环控制行数
            //内层循环控制列数
            //for (int i = 1; i <= 3; i++)
            //{
            //    for (int j = 1; j <= i; j++)
            //    {
            //        Console.Write(j+" ");
            //    }
            //    Console.WriteLine();
            //}
            //for (int j = 1; j <= 9; j++)
            //{
            //    for (int i = 1; i <=j; i++)
            //    {
            //        Console.Write("{0}×{1}={2,-4}",i,j,i*j);
            //    }
            //    Console.WriteLine();
            //}
            #endregion

            #region 一维数组
            //数组定义的语法格式
            //数组的初始化：5称为数组的长度，即数组中包含数据的个数，大括号里面每一个数据称为一个元素
            //new是用来给数组在内存中开辟空间，此种初始化方法称为动态初始化
            //int[] ages=new int[5] { 1,2,3,4,5};
            //ages = new int[] { 1,2,3,4,5};
            //此种情况系统会给数组赋一个默认值：如果数组是数值类型（整型，浮点型），元素的默认值为0，如果是字符串，默认值为空，如果是字符类型，默认值为空，如果是bool类型，默认值是false
            //ages = new int[5];
            //静态初始化 声明和初始化需在一行
            //int[] num = { 1,2,3};

            //double[] scores = new double[2] { 1.2, 3.4 };
            //double[] num1 = new double[] {1.3,4.5 };
            //double[] num2 = { 3.5,6.7};
            //数组作为一个整体，不能直接参与运算，但赋值除外
            //for (int i = ages.Length-1; i >=0; i--)
            //{
            //    Console.WriteLine(ages[i]);
            //}
            //int[] intArr = { 2,3,5,7,11,13,17};
            //int max = intArr[0];
            //int min = intArr[0];
            //for (int i = 0; i < intArr.Length; i++)
            //{
            //    max = max > intArr[i] ? max : intArr[i];
            //    min = min < intArr[i] ? min : intArr[i];
            //}
            //Console.WriteLine("最大值等于：{0}，最小值等于：{1}",max,min);
            #endregion