面试小题

题目不难，总结如下：

1.冒泡排序：

   class Program
    {
        static void Main(string[] args)
        {
            string temp=Console.ReadLine();
            string[] tempArray=temp.Split(' ');
            int[] arry = new int[tempArray.Length];

            for (int i = 0; i < tempArray.Length; i++)
            {
                arry[i] = Convert.ToInt32(tempArray[i]);
                   
            }

            PopSort(arry, true);
            PrintArray(arry);
            PopSort(arry,false);
            PrintArray(arry);
        }

        static void PrintArray(int[] arry)
        {
            for (int i = 0; i < arry.Length ; i++)
            {
                Console.Write("{0} ",arry[i]);
            }
            Console.WriteLine();
        }

        static void PopSort(int[] arry,bool Increase)
        {
            for(int i=0;i<arry.Length-1;i++)
            {
                for (int j = 0; j < arry.Length-1-i; j++)
                {
                    if (Increase)
                    {
                        if (arry[j] > arry[j + 1])
                        {
                            int temp = arry[j];
                            arry[j] = arry[j + 1];
                            arry[j + 1] = temp;
                        }
                    }
                    else
                    {
                        if (arry[j] < arry[j + 1])
                        {
                            int temp = arry[j];
                            arry[j] = arry[j + 1];
                            arry[j + 1] = temp;
                        }
                    }
                }
            }
        }
    }

2.字符串倒置

 class Program
    {
        static void Main(string[] args)
        {
            string temp = Console.ReadLine();
            Console.WriteLine("before convert:{0}", temp);
            StringBuilder sb = new StringBuilder(temp);          
            for (int i = 0; i < sb.Length / 2; i++)
            {
                char c = sb[i];
                sb[i] = sb[sb.Length - i - 1];
                sb[sb.Length - i - 1] = c;
                
            }

            temp = sb.ToString();
            Console.WriteLine("after convert:{0}",temp);


        }
    }

3.二分法查找数组中的某个值

 class Program
    {
        static void Main(string[] args)
        {
            int[] arry = new int[] { 23,45,67,78,100};
            int a=100;
            int b = 23;
            int c = 67;
            int d = 40;
            Console.WriteLine("index of {0} is {1}",a, Find(arry, a));
            Console.WriteLine("index of {0} is {1}",b, Find(arry, b));
            Console.WriteLine("index of {0} is {1}",c, Find(arry, c));
            Console.WriteLine("index of {0} is {1}",d, Find(arry, d));
        }

        static int Find(int[] arry, int value)
        {
            int low = 0;
            int high = arry.Length;
           

            while (low <= high)
            {
                int mid = (low + high) / 2;
                if (arry[mid] == value)
                {
                    return mid;
                }
                else if (arry[mid] < value)
                {
                    low = mid + 1;
                }
                else
                {
                    high = mid - 1;
                }

            }
         
                return -1;
        }
    }

4.输入数字m,n,从1,2,3...n数列中取几个数，使其和等于m，输出所有可能的组合。

class Program
    {
        static void Main(string[] args)
        {
            int m = 15;
            int n = 9;
            int[] arry = new int[n];
            BagProblem(m, n, arry);
        }


        static void printArray(int[] arry)
        {
            for(int i=0;i<arry.Length;i++)
            {
                if(arry[i]==1)
                Console.Write("{0} ",i+1);
            }

            Console.WriteLine();
        }

        static void BagProblem(int m,int n, int[] arry)
        {

            if (n < 1 || m < 1)
            {
                //Console.WriteLine("Invalide input");
                return;
            }
            if (m < n) n = m;
            if (n == m)
            {
                arry[n - 1] = 1;
                printArray(arry);
                //arry[n - 1] = 0;
            }
            arry[n - 1] = 1;
            BagProblem(m - n, n - 1, arry);
            arry[n - 1] = 0;
            BagProblem(m , n - 1, arry);
        }
    }