Remove characters from a String that appears exactly K times

To Remove characters from a String that appears exactly K times, we will create a hash table of all the alphabet elements i.e. a - z, and initialize all values to 0.  Then we'll iterate over given string. We'll increment, value of character by 1 every time we encounter it. Finally, we'll iterate over array again and delete all the characters whose values in our hash table is eual to k.

A formal problem would like this.

Given a string of character of length N remove the character that appears exactly K times in the string. String, N and K will be given as input.

Example input

N = 13
String = hackersfriend
K = 2

Example Output

hacksfind

Here r and e were appearing 2 times so they are removed.

Solution

Let's implement our approach which we discussed in the begining.

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

const int MAX_CHAR = 26; // since chars are a - z

string CleanCharK(string s, int k) 
{ 
	//  make Hash table and initialise to 0 
	int hash[MAX_CHAR] = { 0 }; 
    
    // store the occurance of chars in hash table
	int n = s.length();
	for (int i = 0; i < n; ++i) 
		hash[s[i] - 'a']++; 

	string cleanString = "";  // we'll keep asnwer string here.
  
	for (int i = 0; i < n; ++i) {  
	    
	    // keep only those which dont appear k times 
		if (hash[s[i] - 'a'] != k) { 
			cleanString += s[i]; 
		} 
	} 

	return cleanString; 
} 

 
int main() 
{ 
        
    string s = "hackersfriend";
	int k = 2; 
	cout << CleanCharK(s, k); 

	return 0; 
}