面试题

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication1
{
    class Program
    {

        static void Main(string[] args)
        {
            //冒泡排序
            Console.WriteLine("冒泡排序");
            int[] numbers = { 1, 24, 23, 98, 89, 77, 99, 100 };
            BubbleSort(numbers);
            foreach (int num in numbers)
            {
                Console.Write(num + "  |   ");
            }
            Console.WriteLine("\n请按任意键继续...");

            //递归算法
            Console.WriteLine("递归算法");
            Console.WriteLine(Recursions(9));

            //大小写互转
            Console.WriteLine("递归算法");
            string str = "aaaBBB";
            Console.WriteLine(ToggleCase(str));
            Console.Read();
        }

        /// <summary>
        /// 冒泡排序
        /// </summary>
        /// <param name="numbers"></param>
        public static void BubbleSort(int[] numbers)
        {
            int count = numbers.Length;
            for (int i = 0; i < count; i++)
            {
                for (int j = 0; j < count - 1; j++)
                {
                    if (numbers[j] < numbers[j + 1])
                    {
                        int temp = numbers[j];
                        numbers[j] = numbers[j + 1];
                        numbers[j + 1] = temp;
                    }
                }
            }
        }

        /// <summary>
        /// 递归算法
        /// </summary>
        /// <param name="n"></param>
        public static int Recursions(int n)
        {
            if (n == 1 || n == 2)
            {
                return 1;
            }
            else
            {
                return Recursions(n - 1) + Recursions(n - 2);
            }
        }

        /// <summary>
        /// 大小写互转
        /// </summary>
        /// <param name="str"></param>
        public static string ToggleCase(string str)
        {
            var chars = str.ToCharArray();
            for (int i = 0; i < str.Length; i++)
            {
              
                var cha = chars[i];
                if (cha > 64 && cha < 91)
                {
                    cha = (char)((int)cha + 32);
                }
                else
                {
                    cha = (char)((int)cha - 32);
                }
                chars[i] = cha;
            }
            str = new string(chars);
            return str;
        }
    }
}