CC-8 : Check if characters of the String occur with the same frequency.

Description:

Given input String str, check if all characters of str occur with the same frequency.

Test cases and expected outputs:

Input Parameters	Expected outputs
str="aazzecc";	The characters of the String do not occur at equal frequency
str="aazzcc";	The characters of the String occur at equal frequency
str=" azzccccdddd";	The characters of the String do not occur at equal frequency

Pseudocode:

The java method should accept following input parameters: str (String).

Initialize a variable chrFreqMap of type HashMap to hold characters from str and their counts.

Iterate through str using a for loop with idx as a loop variable with initial value 0 and increment idx till it reaches str.length()-1:

If chrFreqMap does not contain key equal to str.charAt(idx):

Add key str.charAt(idx)and add value 1 to chrFreqMap.

If chrFreqMap contains key equal to str.charAt(idx):

Add key str.charAt(idx)and add value equal to current value of key str.charAt(idx), incremented by 1 to chrFreqMap.

After completion of above loop, chrFreqMap contains all characters of str as keys and the counts of these characters as values.

Using an iterator, iterate through all keys and values of chrFreqMap, if all values are the same, return true from the program, else return false.

Code:

public boolean hashMapSameFreq(String str) throws Exception{
	HashMap<Character,Integer> chrFreqMap=new HashMap<Character, Integer>();
	for (int idx=0; idx < str.length(); idx++) {
		chrFreqMap.put(str.charAt(idx), chrFreqMap.getOrDefault(str.charAt(idx),0)+1);
	}		
	Iterator<Integer> itr=chrFreqMap.values().iterator();
	int frstChrCnt=0; int idx=0; int freq=0;
	while (itr.hasNext()) {
		freq=(Integer)itr.next().intValue();
		if (idx==0) {
			frstChrCnt=freq;
			idx++;
		}else {
			if (freq != frstChrCnt) {
				return false;
			}
		}
	}		
	return true;		
}

Click here to download and run code and test cases !

Below fully running code can be copied and run on Eclipse or other Java IDEs. Refer the classname in code below. If the class name below is "A", save the code below to a file named A.java before running it. Be sure to try your own test cases to enhance your understanding ! You can also tweak the code to optimize or add enhancements and custom features.

import java.util.HashMap;
import java.util.Iterator;


public class HashMapSameFrequency {
	
public boolean hashMapSameFreq(String str) throws Exception{
	HashMap<Character,Integer> chrFreqMap=new HashMap<Character, Integer>();
	for (int idx=0; idx < str.length(); idx++) {
		chrFreqMap.put(str.charAt(idx), chrFreqMap.getOrDefault(str.charAt(idx),0)+1);
	}		
	Iterator<Integer> itr=chrFreqMap.values().iterator();
	int frstChrCnt=0; int idx=0; int freq=0;
	while (itr.hasNext()) {
		freq=(Integer)itr.next().intValue();
		if (idx==0) {
			frstChrCnt=freq;
			idx++;
		}else {
			if (freq != frstChrCnt) {
				return false;
			}
		}
	}		
	return true;		
}
	
	
    
public static void main(String[] args) {
		
	HashMapSameFrequency hp=new HashMapSameFrequency();
	boolean retVal;
	try {
	String str1="aazzecc";
	System.out.println("\n\nThe original string is: "+str1);
	retVal=hp.hashMapSameFreq(str1);
	if (retVal==true) {
		System.out.println("Thhe characters of the String occcur at equal frequency");
	}else {
		System.out.println("The characters of the String do *not* occur at equal frequency");
	}
			
	str1="aazzcc";
	System.out.println("\n\nThe original string is: "+str1);
	retVal=hp.hashMapSameFreq(str1);
	if (retVal==true) {
		System.out.println("Thhe characters of the String occcur at equal frequency");
	}else {
		System.out.println("The characters of the String do *not* occur at equal frequency");
	}
			
	str1="aazzccc";
	System.out.println("\n\nThe original string is: "+str1);
	retVal=hp.hashMapSameFreq(str1);
	if (retVal==true) {
		System.out.println("Thhe characters of the String occcur at equal frequency");
	}else {
		System.out.println("The characters of the String do *not* occur at equal frequency");
	}
	str1="aaz";
	System.out.println("\n\nThe original string is: "+str1);
	retVal=hp.hashMapSameFreq(str1);
	if (retVal==true) {
		System.out.println("Thhe characters of the String occcur at equal frequency");
	}else {
		System.out.println("The characters of the String do *not* occur at equal frequency");
	}
	str1="az";
	System.out.println("\n\nThe original string is: "+str1);
	retVal=hp.hashMapSameFreq(str1);
	if (retVal==true) {
		System.out.println("Thhe characters of the String occcur at equal frequency");
	}else {
		System.out.println("The characters of the String do *not* occur at equal frequency");
	}
	str1="a";
	System.out.println("\n\nThe original string is: "+str1);
	retVal=hp.hashMapSameFreq(str1);
	if (retVal==true) {
		System.out.println("Thhe characters of the String occcur at equal frequency");
	}else {
		System.out.println("The characters of the String do *not* occur at equal frequency");
	}
	str1="aazzcccc";
	System.out.println("\n\nThe original string is: "+str1);
	retVal=hp.hashMapSameFreq(str1);
	if (retVal==true) {
		System.out.println("Thhe characters of the String occcur at equal frequency");
	}else {
		System.out.println("The characters of the String do *not* occur at equal frequency");
	}
	str1="azzccccdddd";
	System.out.println("\n\nThe original string is: "+str1);
	retVal=hp.hashMapSameFreq(str1);
	if (retVal==true) {
		System.out.println("Thhe characters of the String occcur at equal frequency");
	}else {
		System.out.println("The characters of the String do *not* occur at equal frequency");
	}
			
			
	}catch (Exception exception) {
		System.out.print("Exception: "+ exception);
	}
				
}

}