Find the Number of Unique Characters in a String.

In this article, We discuss how to find the number of unique characters in a string using C, C++, Java, and Python.

In these programs, we use for loop and if statement to find the number of unique characters but in python, we use the set function to find unique characters, set is a collection of unique elements there is no duplicate elements.

Here is an example:

Code in C Language:

 #include <stdio.h>
 #include <string.h>

 int main()
 {
    char input[50]="apple";
    int i, j, count=0;
    int n = strlen(input);
     for(i=0; i<n; i++){
        int flag=0;
        for(j=0; j<i; j++){
            if(input[i]==input[j]){
                flag=1;
                break;
            }
        }
        if(flag==0){
            count++;
        } 
    }
    printf("%d",count);

    return 0;
 }

Output:

4

Code in C++:

 #include <iostream>

 using namespace std;

 int main()
 {
    string input = "where";
    int i,j,count=0;
    // cin>>input;
    int n = input.length();
    for(i=0; i<n; i++){
        int flag=0;
        for(j=0; j<i; j++){
            if(input[i]==input[j]){
                flag=1;
                break;
            }
        }
        if(flag==0){
            count++;
        } 
    }
    std::cout << count << std::endl;
    return 0;
 }

Output:

4

Code in Java:

 public class Main
 {
 	public static void main(String[] args) {
 	    String input = "madam";
        int i,j,count=0;
        char arr[]=input.toCharArray();
        int n = arr.length;
        for(i=0; i<n; i++){
        int flag=0;
        for(j=0; j<i; j++){
            if(arr[i]==arr[j]){
                flag=1;
                break;
            }
        }
        if(flag==0){
            count++;
        } 
    }
 		System.out.println(count);
 	}
 }

Output:

3

Code in Python

 str = "session"
 uniqueStr = set(str)
 print(len(uniqueStr))

Output:

5