c#学习笔记1-简单算法

using System;
namespace Demo
{
    class Studycs
    {
        public static void Main(String[] args)
        {
            // String result = Revert("abcdef");
            int[] numbers = { 8, 2, 3, 4, 6 };
            //  int result = searchTree(numbers, 7);

            int[] result=sortSelect(numbers);
            foreach(int item in result)
            {
                Console.WriteLine(item);
            }
            //  char c ='c';
            //  String result = toCompareChar("aABCDEFghiJKm");
           
            Console.ReadKey();
        }

        /// <summary>
        /// 翻转字符串
        /// </summary>
        /// <param name="str"></param>
        /// <returns></returns>
        static String Revert(String str)
        {
            String result = String.Empty;
            char[] array = str.ToCharArray();
            for(int i = array.Length - 1; i >= 0; i--)
            {
                result += array[i];
            }
            return result;
        }

        /// <summary>
        /// 二分查找
        /// </summary>
        /// <param name="array"></param>
        /// <param name="number"></param>
        /// <returns></returns>
        static int  searchTree(int[] array,int number)
        {
            int min =0;
            int max = array.Length-1;
            int index =-1;
            while (max >= min)
            {
                int result = (min + max) / 2;
                if (array[result] == number)
                {
                    index = result;
                    break;
                }
                else if (array[result] > number)
                {
                    max = result - 1;
                }
                else
                {
                    min = result + 1;
                }
            }
            return index;

        }

        /// <summary>
        /// 一维数组最大值
        /// </summary>
        /// <param name="array"></param>
        /// <returns></returns>
        static int Max(int[] array)
        {
            int max =array[0];
            for(int i = 0; i < array.Length; i++)
            {
                if (array[i] > max) max = array[i];
            }
            return max;
        }

        /// <summary>
        /// 查找数组的下标位置
        /// </summary>
        /// <param name="array"></param>
        /// <param name="n"></param>
        /// <returns></returns>

        static int path(int[] array,int n)
        {
            int result = -1;
            for(int i = 0; i < array.Length; i++)
            {
                if (n == array[i]) result = i;
            }
            return result;
        }

        /// <summary>
        /// 查找字符串的下表位置
        /// </summary>
        /// <param name="str"></param>
        /// <param name="c"></param>
        /// <returns></returns>

        static int  searchStr(String str ,char c)
        {
            int result = 0;
            char[] array = str.ToCharArray();
            for(int i = 0; i < array.Length; i++)
            {
                if (c == array[i])
                {
                    result++;
                }
            }
            return result;
        }

        /// <summary>
        /// 平均数
        /// </summary>
        /// <param name="array"></param>
        /// <returns></returns>

        static Double avg(int[] array)
        {
            Double count=0;

            for(int i = 0; i < array.Length; i++)
            {
                count += array[i];
            }

            return count / array.Length;
        }

        /// <summary>
        /// 选择排序
        /// </summary>
        /// <param name="array"></param>
        /// <returns></returns>
        static int[] sortSelect(int[] array)
        {
            for(int i =0; i < array.Length - 1; i++)
            {
                for(int j=i+1; j < array.Length; j++)
                {
                    if (array[i] > array[j])
                    {
                        int temp = array[i];
                        array[i] = array[j];
                        array[j] = temp;
                    }
                }
            }
            return array;
        }


        /// <summary>
        /// 大小写字符转换
        /// </summary>
        /// <param name="str"></param>
        /// <returns></returns>
        static String toCompareChar(String str)
        {
            String result ="";
            char[] array = str.ToCharArray();
            for(int i=0; i < array.Length; i++)
            {
                if(array[i]>='A' && array[i] <= 'Z')
                {
                    result += Convert.ToChar(array[i] + 32);
                }
                if (array[i] >= 'a' && array[i] <= 'z')
                {
                    result += Convert.ToChar(array[i] -32);
                }
            }
            return result;

        }
    }
}