CountingDuplicateCharacters.java

// Time Complexity: O(n)
// Space Complexity: O(n)
// n is the length of the string

// In JAVA

import java.util.HashMap;
import java.util.Map;

class Definition {
    public static Map<Character, Integer> countDuplicateCharacters(String string) {
        var resultMap = new HashMap<Character, Integer>();
        // write your code here ...
        for(int i=0; i<string.length(); ++i) {
            if(string.charAt(i) == ' ') continue;
            if(resultMap.containsKey(string.charAt(i))) {
                resultMap.put(string.charAt(i), resultMap.get(string.charAt(i))+1);
            } else {
                resultMap.put(string.charAt(i), 1);
            }
        }
        return resultMap;
    }
}

class Duplicates {

    public static void main(String[] args) {
        String message = "Competitive Programming Can Be A Little Bit Tricky!";
        Definition definition = new Definition();
        System.out.println(definition.countDuplicateCharacters(message));
/*
        definition.countDuplicateCharacters(message).entrySet().forEach(entry -> {
            if(entry.getValue() == 1 ) {
                System.out.println(entry.getKey());
            }
        });
*/
    }
}

// In C++

#include<bits/stdc++.h>
using namespace std;

unordered_map<char, int> countDuplicateCharacters(string);

int main() {
	int count=0;
	// Printing map
	for(auto items : countDuplicateCharacters("Competitive Programming Can Be A Little Bit Tricky!")) {
		if(items.second > 1) {
			count++;
			cout << items.first << " " << items.second  << endl;
		}
	}
	if(count==0) cout << "No Characters Are Repeating" << endl;
}

// Definition
unordered_map<char, int> countDuplicateCharacters(string str) {
	unordered_map<char, int> resultMap;
	for(auto chars : str) {
		//ignoring space
		if(chars == ' ') continue;
		resultMap[chars]++;
	}
	return resultMap;
}