How to print duplicate characters in a String using C#?

Set maximum value for char.

static int maxCHARS = 256;

Now display the duplicate characters in the string.

String s = "Welcometomywebsite!"; int []cal = new int[maxCHARS]; calculate(s, cal); for (int i = 0; i < maxCHARS; i++) if(cal[i] > 1) {    Console.WriteLine("Character "+(char)i);    Console.WriteLine("Occurrence = " + cal[i] + " times"); }

Above, we have calculated the frequency of characters. The same is shown below in the complete example −

Example

using System; class Demo {    static int maxCHARS = 256;    static void calculate(String s, int[] cal) {       for (int i = 0; i < s.Length; i++)       cal[s[i]]++;    }    public static void Main() {       String s = "Welcometomywebsite!";       int []cal = new int[maxCHARS];       calculate(s, cal);       for (int i = 0; i < maxCHARS; i++)       if(cal[i] > 1) {          Console.WriteLine("Character "+(char)i);          Console.WriteLine("Occurrence = " + cal[i] + " times");       }    } }