【C#】常见的程式面试考题

废话不多说，程式实务直接开干!

学习目标: 程式面试的实务

学习难度: ☆☆☆

Binary Search

using System;using System.Collections.Generic;namespace ConsoleApp1{    public class MainProgram    {        static int BinarySearch(int[] array,int target)        {            int min = 0;            int max = array.Length - 1;            while(min<=max)            {                int mid = (min + max) / 2;                if (target == array[mid]) return mid;                if (target < array[mid]) max = mid - 1;                if (target > array[mid]) min = mid + 1;            }            return -1;        }        static void Main(string[] args)        {            int[] array = { 1, 3, 5, 7, 9 };            Console.WriteLine(BinarySearch(array, 9));        }    }}

Fibonacci

using System;using System.Collections.Generic;namespace ConsoleApp1{    public class MainProgram    {        static int Fibonacci(int num)        {            if (num == 0) return 0;            if (num == 1) return 1;            return Fibonacci(num-1)+Fibonacci(num-2);        }        static void Main(string[] args)        {            Console.WriteLine(Fibonacci(13));        }    }}

DownStairs

using System;using System.Collections.Generic;namespace ConsoleApp1{    public class MainProgram    {        public static long DownStairs(int n)        {            if(n==1)            {                return 1;            }            else if(n==2)            {                return 2;            }            else            {                return DownStairs(n - 2) + DownStairs(n - 1);            }        }        public static void Main(string[] args)        {            Console.WriteLine(DownStairs(4));        }    }}

Maximum Subarray

using System;using System.Collections.Generic;namespace ConsoleApp1{    public class MainProgram    {        public static int GetMax(int[] array)        {            int sum = 0;            int max = array[0];            for (int i = 0; i < array.Length; ++i)            {                sum += array[i]; //计算阵列中连续数的总和(0~4 ~ 4~4)                sum = Math.Max(0, sum); //排除掉负数的加总                max = Math.Max(sum, max); //判断当前与上一个加总哪个较大            }            return max;        }        static void Main(string[] args)        {            int[] array = {1,7,-70,30,30};            Console.WriteLine(GetMax(array));        }    }}

Bubble Sort

using System;using System.Collections.Generic;namespace ConsoleApp1{    public class MainProgram    {        public static int[] BubbleSort(int[] array)        {            int temp;            for (int i = 0; i < array.Length; ++i)            {                for (int j = i+1; j < array.Length; ++j)                {                    if(array[i]>array[j])                    {                                             temp = array[j];                        array[i] = array[j];                        array[j] = temp;                    }                }                          }            return array;        }        static void Main(string[] args)        {            int[] array = {3,1,7,2,4,9};            array = BubbleSort(array);            foreach (var item in array)            {                Console.WriteLine(item+"\n");            }        }    }}

Swap two variables without temp

using System;using System.Collections.Generic;namespace ConsoleApp1{    public class MainProgram    {        static void Main(string[] args)        {            int a = 5;            int b = 10;                        //XOR做运算            a = a ^ b;            b = a ^ b;            a = a ^ b;            Console.WriteLine("a"+a+","+"b"+b);        }    }}

sum the Integers (1 to N)

using System;using System.Collections.Generic;namespace ConsoleApp1{    public class MainProgram    {        static int Sum(int last)        {            int first = 1;            return  (first+last)*last/ 2;        }        static void Main(string[] args)        {            Console.WriteLine(Sum(100));        }    }}

sum the Integers (1x2+2x3+3x4+...(n-1)xn)

using System;using System.Collections.Generic;namespace ConsoleApp1{    public class MainProgram    {        static int Sum(int n)        {            int sum=0;            for (int i = 2; i < n; i++)            {                sum += (i - 1) * i;            }            return sum;        }        static void Main(string[] args)        {            Console.WriteLine(Sum(100));        }    }}

sum the Integers (1X1+2X2+3X3+...+nxn)

using System;using System.Collections.Generic;namespace ConsoleApp1{    public class MainProgram    {        static int Sum(int n)        {            int sum=0;            for (int i = 1; i <= n; i++)            {                sum += i * i;            }            return sum;        }        static void Main(string[] args)        {            Console.WriteLine(Sum(100));        }    }}

Find a max number in unsort array

using System;using System.Collections.Generic;namespace ConsoleApp1{    public class MainProgram    {        static int FindMax(int[] array)        {            int max = 0;            for (int i = 0; i < array.Length; i++)            {                if (array[i] > max) max = array[i];            }            return max;        }        static void Main(string[] args)        {            int[] array = new int[] { 1, 5, 7, 11, 2, 4, 9, 20, 23, 8, 13, 30, 6 };            Console.WriteLine(FindMax(array));        }    }}

Find a second max number in unsort array

using System;using System.Collections.Generic;namespace ConsoleApp1{    public class MainProgram    {        static int FindSecondMax(int[] array)        {            int max= 0;            int second = 0;            for (int i = 0; i < array.Length; i++)            {                int temp = array[i];                if (temp > max)                {                    second = max; max = temp;                 }                else if (temp > second) second = temp;            }            return second;        }        static void Main(string[] args)        {            int[] array = new int[] { 1, 5, 7, 11, 2, 4, 9, 20, 23, 8, 13, 30, 6 };            Console.WriteLine(FindSecondMax(array));        }    }}

Find the missing integer in array

using System;using System.Collections.Generic;namespace ConsoleApp1{    public class MainProgram    {        static int Sum(int[] array)        {            int sum=0;            for (int i = 0; i < array.Length; i++)            {                sum += array[i];            }            return sum;        }        static void Main(string[] args)        {            int[] array = new int[] { 1,2,3,4,6,7,8 };            int result = ((array[0] + array[array.Length-1]) * (array.Length + 1) / 2) - Sum(array);            Console.WriteLine(result);        }    }}

Find the larger number without judgement statements

using System;namespace ConsoleApp1{    public class MainProgram    {        static int max(int a, int b)        {            return ((a + b) + Math.Abs((a - b))) / 2;        }        static void Main(string[] args)        {            Console.WriteLine(max(1, 3));        }    }}

参考资料:

https://emn178.pixnet.net/blog/post/92389195