C++ Basic Program Examples | Count (frequency) of character

In this post we will try to find out the frequency(count) of each character in a given string.

Method1:

Prerequisites: Basic knowledge of array, string and ASCII value.

let's talk about the question:

We have a string of either lowercase or uppercase characters. that means string must have all characters from lowercase or uppercase:

eg:"earth", "EARTH"

Now we have to find the frequency(count) of each character of the given string;

eg:"babsur"

freq of "a" = 1;

freq of "b" = 2;

freq of "r" =1;

freq of "s" = 1;

freq of "u" = 1;

let's write the code:

#include<bits/stdc++.h>

using namespace std;

int  main(){

string s;

cin>>s;

int freq[26] = {0};

for(int i=0;i<s.size();i++){

       freq[s[i]-'a']++; // for lowercase string use s[i]-'a';

      }

for(int i=0;i<26;i++){

if(freq[i]!=0){

       cout<<"freq of "<<char(97+i)<<":"<<freq[i]<<endl;

}

}

}

Above written code is for those string which only have lowercase alphabets.

For better understanding go through the above image:

if we have a string of upper case alphabets. then we have to change our code.

everything will remain same, only make change in both for loop:

In first for loop:

freq[s[i]-'A']++;

In second for loop:

if(freq[i]!=0){

  cout<<"freq of "<<char(65+i)<<":"<<freq[i]<<endl;

}

this is the first method.

Method2:

Use hashmap:

#include<bits/stdc++.h>

using namespace std;

int main(){

string s;

cin>>s;

map<char,int>m;

for(int i=0;i<s.size();i++){

   if(m.find(s[i])!=m.end()){

     auto it = m.find(s[i]);

     it->second++;

}

m.insert(make_pair(s[i],1);

}

for(auto it = m.begin(); it != m.end(); it++){

     cout<<"freq of  "<<it->first<<":"<<it->second<<endl;

}

}