C method question 1

1. Palindrome refers to a string that reads both forward and backward . Write a method , Judging a string str1, Is it a palindrome , Is a palindrome that returns true, Otherwise return to false. Like strings b yes ag7ga It's palindrome. , And strings abc6es It's not palindrome . Require application writing , To test the correctness of the method .

 public static bool huiwen(string s)
        {
    
            bool a;
            string str = null;
            for (int i = s.Length - 1; i >= 0; i--)
            {
    
                str += s[i];
            }
            if (str == s)
            {
    
                a = true;
            }
            else
                a = false;
                return a;
        }

           string s = Console.ReadLine();
            bool a = huiwen(s);
            if (a == true)
                Console.WriteLine(" It's palindrome. ");
            else
                Console.WriteLine(" Not a palindrome ");
                Console.ReadLine();

2. Write a method , Count the number of words in a string , The return value is the number of words . Specify that words are separated by several spaces . For example, if you enter a string " I am a student ", The result is 4. Require application writing , To test the correctness of the method .

public static int words(string s)
        {
    
            int count = 1;
            for (int i = 0; i < s.Length; i++)
            {
    
                *****if (s[i] == ' ' && s[i + 1] != ' ')*****
                {
    
                    count++;
                }
            }
            return count;
        }

            string s = Console.ReadLine();
            int a = words(s);
            Console.WriteLine(" The number of words is {0}", a);
            Console.ReadLine();

3. Write a method , Judge whether a positive integer is a prime number , The return value is of boolean type . Require application writing , seek 1-100 All the prime Numbers between .

  public static bool sushu(int a)
        {
    
          
            for (int i = 2; i < a; i++)
            {
    
                if (a % i == 0)
                {
    
                    return false;
                }
                
            }
            return true;
        }

 public static void Main(string[] args)
        {
    
            int aaa =int.Parse(Console.ReadLine());
            if (sushu(aaa) == true)
            {
    
                Console.WriteLine(" Prime number ");
            }
            else
                Console.WriteLine(" Not primes ");
            for (int i = 1; i < 100; i++)
            {
    
                if (sushu(i) == true)
                    Console.WriteLine(i);

            }

4. Enter a string , Statistics string Chinese and English letters 、 Number of numeric characters and other symbols and output . Require application writing , To test the correctness of the method .

 static void Letterdigitfuhao(string st)
        {
    
            string ssletter = "";
            string ssdigit = "";
            string ssfuhao = "";
            int letter = 0;
            int digit = 0;
            int fuhao = 0;
            for (int i = 0; i < st.Length; i++)
            {
    
                ***if (char.IsLetter(st[i]))***
                {
    
                    letter++;
                    ssletter += st[i];
                }
                else if (char.IsDigit(st[i]))
                {
    
                    digit++;
                    ssdigit += st[i];
                }
                else
                {
    
                    fuhao++;
                    ssfuhao += st[i];
                }
            }
            Console.WriteLine(" The number of letters is {0} individual , Among them is {1}", letter, ssletter);
            Console.WriteLine(" The number is {0} individual , Among them is {1}", digit, ssdigit);
            Console.WriteLine(" The number of other symbols is {0} individual , Among them is {1}", fuhao, ssfuhao);
        }

public  static void Main(string[] args)
        {
    
            Console.WriteLine(" Please enter a string ：");
            string st = Console.ReadLine();
            Letterdigitfuhao(st);
            Console.ReadLine();
        }

5. Write a method , Right integer m Sum up , The summation formula is s= 1/2+1/3+…+1/m, Method returns s Value . Require application writing , To test the correctness of the method .

 public static double ssum(double n)
        {
    
            double sum = 0;
           
            for (double i = 1; i < n; i++)
            {
    
                sum += 1 / (i + 1);
            }
            return sum;

        }

          double aaa =double.Parse( Console.ReadLine());
            Console.WriteLine(ssum(aaa));

public static string AddDollar(string sentence)
        {
    
            string st = string.Empty;
            for (int i = 0; i < sentence.Length; i++)
            {
    
                ***if (char.IsLetter(sentence[i]))***
                {
    
                    st += sentence[i] + "$";
                }
                else
                {
    
                    st += sentence[i];
                }
            }
            return st;
        }

            string st = Console.ReadLine();
            Console.WriteLine(" Add ￥ The result is {0}", AddDollar(st));

6. Write a method , Add one after all English characters in a string $ character , And return the processed string . For example, the input ：A1B23CD45, The return value of the method is ：A$1B$23C$D$45, Require application writing , To test the correctness of the method .

 public static string AddDollar(string sentence)
        {
    
            string st = string.Empty;
            for (int i = 0; i < sentence.Length; i++)
            {
    
                ***if (char.IsLetter(sentence[i]))***
                {
    
                    st += sentence[i] + "$";
                }
                else
                {
    
                    st += sentence[i];
                }
            }
            return st;
        }

public  static void Main(string[] args)
        {
    
            Console.WriteLine(" Please enter a string ：");
            string st = Console.ReadLine();
            Console.WriteLine(" Add ￥ The result is {0}", AddDollar(st));
        }

7. Write a method , Delete all lowercase characters in the string , The rest of the characters remain unchanged . Method returns the converted String .str=“AbC” Change to string to =“AC”, Require application writing , To test the correctness of the method .

 public static string Dellower(string stt)
        {
    
            string st1 = string.Empty;
            for (int i = 0; i < stt.Length; i++)
            {
    
                if (char.IsUpper(stt[i]))
                {
    
                    st1 += stt[i];
                }
            }
            return st1;
        }

public  static void Main(string[] args)
        {
    
            Console.WriteLine(" Please enter a string :");
            string sttttt = Console.ReadLine();
            Console.WriteLine(Dellower(sttttt));
            Console.ReadLine();
        }

8. Write a method , For a string , Encrypt according to the following rules ： If it is an English letter, capital will change to lowercase 、 Lowercase to uppercase , For non English characters, it remains unchanged . The return value is to return the encrypted string . Require application writing , To test the correctness of the method .

 public static string UpperLowerDigit(string stt)
        {
    
            string st = string.Empty;
            for (int i = 0; i < stt.Length; i++)
            {
    
                if (char.IsUpper(stt[i]))
                {
    
                    st += char.ToLower(stt[i]);
                }
                else if (char.IsLower(stt[i]))
                {
    
                    st += char.ToUpper(stt[i]);
                }
                else if (char.IsDigit(stt[i]))
                {
    
                    st += stt[i];
                }
            }
            return st;
        }

public  static void Main(string[] args)
        {
    
            Console.WriteLine(" Please enter a string :");
            string st = Console.ReadLine();
            Console.WriteLine(UpperLowerDigit(st));

            Console.ReadLine();
        }

9. Write a method , Find two integers m and n Maximum common divisor of , And return... As a return value . Require application writing , To test the correctness of the method .

public static int Gongyushu(int m, int n)
        {
    
            int gys = 0;
            int temp = 0;
            if (m < n)
            {
    
                temp = m;
                m = n;
                n = temp;

            }
            ***for (int i = n; i > 0; i--)***
            {
    
                ***if (m % i == 0 && n % i == 0)***
                {
    
                    gys = i;
                    break;
                }
            }
            return gys;
        }

public  static void Main(string[] args)
        {
    
            Console.WriteLine(" Find two integers m and  n  Maximum common divisor of ");
            int m = int.Parse(Console.ReadLine());
            int n = int.Parse(Console.ReadLine());
            Console.WriteLine(Gongyushu(m, n));

            Console.ReadLine();
        }

10. Write a method , Find two integers m and n The least common multiple of , And return... As a return value . Require application writing , To test the correctness of the method .

 public static int Gongbeishu(int m, int n)
        {
    
            int gys = 0;
            int temp = 0;
            if (m < n)
            {
    
                temp = m;
                m = n;
                n = temp;
            }
            for (int i = m; i <= m * n; i++)
            {
    
                if (i % m == 0 && i % n == 0)
                {
    
                    gys = i;
                    break;
                }
            }
            return gys;
        }

public  static void Main(string[] args)
        {
    
            Console.WriteLine(" Find two integers m and  n  Maximum common divisor of ");
            int m = int.Parse(Console.ReadLine());
            int n = int.Parse(Console.ReadLine());
            Console.WriteLine(Gongbeishu(m, n));
            Console.ReadLine();
        }

11. Write a method , seek s=1/a+1/aa+1/aaa+1/aaaa+1/aa…a Value , among a Is a user-defined number . for example 1/2+1/22+1/222+1/2222+1/22222( At this time, there is 5 Add up the numbers ), The return values are and s. Require application writing , To test the correctness of the method .

 ***public static double Aaaaa(double aa, int nn)***
        {
    
            double s = 0;
            double b = 1;
            for (int i = 1; i < nn; i++)
            {
    
                b = b * 10 + 1;
                s += 1 / (b * aa);
            }
            return s + 1 / aa;
        }

 public  static void Main(string[] args)
        {
    
            Console.WriteLine(" Please enter a number a(a yes 1-9 Number between ):");
            double aaa = double.Parse(Console.ReadLine());
            Console.WriteLine(" frequency ：");
            int nnnn = int.Parse(Console.ReadLine());
            Console.WriteLine(Aaaaa(aaa, nnnn));
            Console.ReadLine();
        }

12. Write a method , Judge whether a number is perfect , The return value is of boolean type . If a number is exactly equal to the sum of its factors , This number is called “ Complete ”. for example 6=1＋2＋3. Require application writing , To test the correctness of the method .

 public static bool wanshu(double n)
        {
    
            double sum = 0;
            for (int i = 1; i < n; i++)
            {
    
                if (n % i == 0)
                {
    
                    sum += i;
                }
            }
            if (sum == n)
                return true;
            else
            return false;
        }

double aaa = double.Parse(Console.ReadLine());
            Console.WriteLine(wanshu(aaa));