C simple question 2

13. seek n within （ barring n） Can't be 2 and 5 to be divisible by （ Can be 2 perhaps 5 Divisible but not divisible at the same time ） The square root of the sum of all natural numbers s,n Input from keyboard .

Console.WriteLine(" Please enter n");
            int n = int.Parse(Console.ReadLine());
            int sum = 0;
            for(int i=0;i<n;i++)
            {
    
                if(i%2!=0&&i%5!=0)
                {
    
                    sum += i;
                    
                }               
            }
            double s = Math.Sqrt(sum);
            Console.WriteLine(s);

14. Input 1~7 A number between , Output its corresponding day of the week . For example, the input 1 Output Monday.

Console.WriteLine(" Please enter 1-7 Number between ：");
            int n = int.Parse(Console.ReadLine());
            switch(n%10)
            {
    
                case 1: Console.WriteLine("Monday");
                    break;
                case 2:
                    Console.WriteLine("Tuesday");
                    break;
                case 3:
                    Console.WriteLine("Wednesday");
                    break;
                case 4:
                    Console.WriteLine("Thursday");
                    break;
                case 5:
                    Console.WriteLine("Friday");
                    break;
                case 6:
                    Console.WriteLine("Saturday");
                    break;
                case 7:
                    Console.WriteLine("Sunday");
                    break;
                default:Console.WriteLine(" There is an error in your input ！");
                    break;
            }

15. The single digit is 8 And can be 4 Divide but not be 7 How many two digit natural numbers are there in total , Number of Statistics , And output these numbers .

int count = 0;
            for(int i=10;i<100;i++)

            {
    
                if(i%10==8&&i %4==0&&i%7!=0)
                {
    
                    Console.Write("{0} ", i);
                    count++;
                    
                }
            }
            Console.WriteLine(" share {0} individual ",count);

16. Enter a string , use foreach Statement to calculate the length of the input string , And display the length .

Console.WriteLine(" Please enter a string ：");
            string st = Console.ReadLine();
            int count = 0;
            foreach(char c in st) 
            {
    
                Console.Write("{0} ",c);
                count++;
            }
            Console.WriteLine(" The length is ：{0}",count);

17. Input 7 Number , Count the positive numbers respectively 、 negative 、 The number of zeros .

            int[] marry = new int[7];
            for (int i = 0; i < marry.Length; i++)
            {
    
                marry[i] = int.Parse(Console.ReadLine());
            }
            int zs = 0;
            int fs = 0;
            int zero = 0;
            for (int i = 0; i < marry.Length; i++)
            {
    

                if (marry[i] > 0)
                    zs++;
                else if (marry[i] < 0)
                    fs++;
                if (marry[i] == 0)
                    zero++;
            }
            Console.Write(" Positive numbers have {0} individual , Negative numbers have {1} individual ,0 Yes {2} individual ", zs, fs, zero);

18. Calculation ：1/2+2/3-3/4+4/5…… front 50 term .

            double sum = 0;
            for (double i = 1; i <= 50; i++)
            {
    
                sum += Math.Pow(-1, i + 1) * i / (i + 1);
            }
            Console.WriteLine("1/2+2/3-3/4+4/5…… front 50 Items for {0}", sum);
            Console.ReadLine();

19. Fei's sequence is A.D 13 Invented by the mathematician fiboracci in the th century . namely ：1,2,3,5,8,13,21,34,55,89,……, Output ratio 144 The big one, the smallest one .

 int a = 1;
            int b = 2;
            int c = 3;
            while (c < 144)
            {
    
                a = b;
                b = c;
                c = a + b;
            }
            Console.WriteLine(c+b);

20. Input some integers from the terminal , Find out more than 0 Number of numbers , And output these numbers and their average .

Console.WriteLine(" Please enter some integers ：");
            int[] a = new int[5];
            for (int i = 0; i < a.Length; i++)
            {
    
                a[i] = int.Parse(Console.ReadLine());
            }
            double sum = 0;
            double avg = 0;
            int count = 0;

            for(int i=0;i<a.Length;i++)
            {
    
                if (a[i] > 0)
                {
    
                    sum += a[i];
                    count++;
                    avg = sum / count;
                }
            }
            Console.WriteLine(" The average value is {0}",avg);

21. Receive a real number entered by the user N, The absolute value of the real number is calculated and output by programming without using the function of calculating the absolute value .

Console.WriteLine(" Please enter a positive integer N：");
            int N = int.Parse(Console.ReadLine());
            int a;
            if (N ==0)
                Console.WriteLine("0 No absolute value ！");
            else if (N > 0)
                Console.WriteLine("N The absolute value of is ：{0}", N);
            else
                Console.WriteLine("N The absolute value of is ：{0}", N * (-1));

. Receive a positive integer entered by the user N, seek 1-2+3-4…+N And output .

            Console.WriteLine(" Please enter a positive integer N：");
            int a = int.Parse(Console.ReadLine());
            double sum = 0;
            for(int i=0;i<=a;i++)
            {
    
                sum += Math.Pow(-1,i+1)*i;//（ base number , Power number ）

            }
            Console.WriteLine(" seek 1-2+3-4…+N Value ：{0}", sum);

23. Receive a positive integer entered by the user N, Calculation 1 To N The cube and .

Console.WriteLine(" Please enter a positive integer ：");
            int a = int.Parse(Console.ReadLine());
            double sum = 0;
            for(int i=0;i<=a;i++)
            {
    
                sum += i * i*i ;

            }
            Console.WriteLine(" Cube sum is ：{0}",sum);

24. Receive two numbers entered by the user , Judge whether two numbers can be divisible .

Console.WriteLine(" Please enter two numbers ：");
            int a = int.Parse(Console.ReadLine());
            int b = int.Parse(Console.ReadLine());
            if (a % b == 0||b%a==0)
            {
    
                Console.WriteLine(" aliquot ");

            }
            else
                Console.WriteLine(" Not divisible ");