几个适合面试的小算法

1. 将字符串“I am a good man” 输出为：“man good a am I”

using System;

namespace ConsoleApplication3
{
    class Program
    {
        static void Main(string[] args)
        {
            string str = "I am a good man";
            string[] arrayStr = str.Split(' '); //将字符串截取后存入数组中

            Array.Reverse(arrayStr);  //反序数组元素
            foreach (var item in arrayStr)
            {
                Console.WriteLine(item);
            }
            Console.ReadLine();
        }
    }
}

2.  有一列数1，1，2，3，5，........求第30个数. (用递归)  这个代码遍地都是，不解释......

using System;

namespace ConsoleApplication2
{
    class Program
    {
        static void Main(string[] args)
        {

            Console.WriteLine(Foo(30));

            Console.ReadLine();
        }

        public static int Foo(int i)
        {
            if (i <= 0)
            {
                return 0;
            }
            else if (i > 0 && i <= 2)
            {
                return 1;
            }
            else
            {
                return Foo(i - 1) + Foo(i - 2);
            }
        }
    }
}

3.有一组字符串，要求输入每种组合，例如：数组{"a","b","c"}输出组合为：ab ac ,ba bc, ca cb

using System;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            string[] objstr = new string[]

            {
                "a","b","c","d","e","f","g"
            };

            for (int i = 0; i < objstr.Length; i++)
            {
                Console.WriteLine("第{0}组组合为：", i + 1);
                for (int j = 0; j < objstr.Length; j++)
                {
                    if (objstr[i] != objstr[j])
                    {
                        Console.Write(objstr[i] + objstr[j] + " ");
                    }
                    if (j == objstr.Length - 1)
                    {
                        Console.Write("\n\n");
                    }
                }
            }

            Console.ReadLine();
        }
    }
}

4.打印5000以内的对称数：如 11,111,121,1221（华为面试题）

 

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

namespace DuiShu
{
    class Program
    {
        static void Main(string[] args)
        {

            GetA(5000);

            Console.ReadLine();
        }

        private static void GetA(int maxValue)
        {
            string temp = String.Empty;
            string partA = String.Empty;
            string partB = String.Empty;
            int index = 0;

            for (int i = 0; i <= maxValue; i++)
            {
                if (i > 10)
                {
                    temp = i.ToString();

                    index = temp.Length / 2;

                    if (temp.Length % 2 == 0)
                    {
                        partA = temp.Substring(0, index);
                        partB = temp.Substring(index, index);
                    }

                    else
                    {
                        partA = temp.Substring(0, index);
                        partB = temp.Substring(index + 1, index);
                    }

                    if ((index == 1 && partA.Equals(partB)) ||
                        (index > 1 && partA.Equals(String.Concat(partB.ToArray().Reverse()))))
                    {
                        Console.WriteLine(temp);

                        continue;
                    }
                }
            }
        }
    }
}