C#语言基础

lesson#4 排序算法+二维数组

内容：

1. 选择排序；

2. 二维数组；

3. Foreach循环；

1. 选择排序；

//练习题1：

//用选择排序法排列数组下列数组并打印排序后的数组：

            double[] arr = { 12, 90, 14, 85, 34, 9, 23, 55, 10.5, 8 };

            for (int i = 0; i < arr.Length - 1; i++)

            {

                for (int j = i + 1; j < arr.Length; j++)

                {

                    if (arr[i] > arr[j])

                    {

                        double temp = arr[i];

                        arr[i] = arr[j];

                        arr[j] = temp;

                    }

                }

            }

            foreach (double a in arr) { Console.WriteLine(a); }

2. 二维数组；

//有两下标的数组称为二维数组

            int[] a;

//动态初始化

            int[,] b = new int[2, 3] { { 1, 2, 3 }, { 4, 5, 6 } };

            //b = new int[,] { { 1, 2, 3 }, { 4, 5, 6 } };

            //b = new int[2, 3];

//静态初始化

            int[,] c = { { 1, 2, 3 }, { 4, 5, 6 } };

            //Console.WriteLine(b[1,1]);

            b[1, 0] = 7;

            for (int i = 0; i < b.GetLength(0); i++)

            {

                //i=0,1

                for (int j = 0; j < b.GetLength(1); i++)

                {

                    Console.Write(b[i, j]);

                }

                Console.WriteLine();

            }

//练习

//将一个二维数组的行和列交换，存储到另外一个数组中去

            int[,] arr = new int[2, 3] { { 1, 2, 3 }, { 4, 5, 6 } };

            int[,] brr = new int[arr.GetLength(1), arr.GetLength(0)];

            for (int i = 0; i < brr.GetLenth(0); i++)

            {

                for (int j = 0; j < brr.GetLenth(1); j++)

                {

                    brr[i, j] = arr[j.i];

                    Console.Write(brr[i, j]);

                }

            }

            Console.WriteLine();

3. foreach循环；

int[] a = { 1, 2, 3, 4, 5 };

            int[,] b = { { 1, 2, 3 }, { 4, 5, 6 } };

            foreach (var item in a)

            {

                Console.WriteLine(item);

            }