Print characters and their frequencies in order of occurrence

Given a string str containing only lowercase characters. The problem is to print the characters along with their frequency in the order of their occurrence and in the given format explained in the examples below.

Examples:

Input : str = "geeksforgeeks"
Output : g2 e4 k2 s2 f1 o1 r1

Input : str = "elephant"
Output : e2 l1 p1 h1 a1 n1 t1

Source: SAP Interview Experience | Set 26

Recommended: Please try your approach on {IDE} first, before moving on to the solution.

Approach: Create a count array to store the frequency of each character in the given string str. Traverse the string str again and check whether the frequency of that character is 0 or not. If not 0, then print the character along with its frequency and update its frequency to 0 in the hash table. This is done so that the same character is not printed again.

C++

// C++ implementation to print the character and 
// its frequency in order of its occurrence 
#include <bits/stdc++.h> 
using namespace std; 
  
#define SIZE 26 
  
// function to print the character and its frequency 
// in order of its occurrence 
void printCharWithFreq(string str) 
{ 
    // size of the string 'str' 
    int n = str.size(); 
  
    // 'freq[]' implemented as hash table 
    int freq[SIZE]; 
  
    // initialize all elements of freq[] to 0 
    memset(freq, 0, sizeof(freq)); 
  
    // accumulate freqeuncy of each character in 'str' 
    for (int i = 0; i < n; i++) 
        freq[str[i] - 'a']++; 
  
    // traverse 'str' from left to right 
    for (int i = 0; i < n; i++) { 
  
        // if frequency of character str[i] is not 
        // equal to 0 
        if (freq[str[i] - 'a'] != 0) { 
  
            // print the character along with its 
            // frequency 
            cout << str[i] << freq[str[i] - 'a'] << " "; 
  
            // update frequency of str[i] to 0 so  
            // that the same character is not printed  
            // again 
            freq[str[i] - 'a'] = 0; 
        } 
    } 
} 
  
// Driver program to test above 
int main() 
{ 
    string str = "geeksforgeeks"; 
    printCharWithFreq(str); 
    return 0; 
} 

Java

// Java implementation to print the character and 
// its frequency in order of its occurrence 
public class Char_frequency { 
      
    static final int SIZE = 26; 
       
    // function to print the character and its  
    // frequency in order of its occurrence 
    static void printCharWithFreq(String str) 
    { 
         // size of the string 'str' 
        int n = str.length(); 
  
        // 'freq[]' implemented as hash table 
        int[] freq = new int[SIZE]; 
  
        // accumulate freqeuncy of each character 
        // in 'str' 
        for (int i = 0; i < n; i++) 
            freq[str.charAt(i) - 'a']++; 
  
        // traverse 'str' from left to right 
        for (int i = 0; i < n; i++) { 
  
            // if frequency of character str.charAt(i) 
            // is not equal to 0 
            if (freq[str.charAt(i) - 'a'] != 0) { 
  
                // print the character along with its 
                // frequency 
                System.out.print(str.charAt(i)); 
                System.out.print(freq[str.charAt(i) - 'a'] + " ");  
  
                // update frequency of str.charAt(i) to  
                // 0 so that the same character is not 
                // printed again 
                freq[str.charAt(i) - 'a'] = 0; 
            } 
        } 
    } 
       
    // Driver program to test above 
    public static void main(String args[]) 
    { 
        String str = "geeksforgeeks"; 
        printCharWithFreq(str); 
    } 
} 
// This code is contributed by Sumit Ghosh 

Python3

# Python3 implementation to pr the character and 
# its frequency in order of its occurrence 
  
# import library 
import numpy as np 
  
# Function to print the character and its  
# frequency in order of its occurrence 
def prCharWithFreq(str) : 
      
    # Size of the 'str' 
    n = len(str) 
      
    # Initialize all elements of freq[] to 0 
    freq = np.zeros(26, dtype = np.int) 
  
    # Accumulate freqeuncy of each  
    # character in 'str' 
    for i in range(0, n) : 
        freq[ord(str[i]) - ord('a')] += 1 
                  
    # Traverse 'str' from left to right 
    for i in range(0, n) : 
          
        # if frequency of character str[i]   
        # is not equal to 0 
        if (freq[ord(str[i])- ord('a')] != 0) : 
              
            # print the character along  
            # with its frequency 
            print (str[i], freq[ord(str[i]) - ord('a')],  
                                                end = " ") 
  
            # Update frequency of str[i] to 0 so that 
            # the same character is not printed again 
            freq[ord(str[i]) - ord('a')] = 0
          
      
# Driver Code 
if __name__ == "__main__" : 
      
    str = "geeksforgeeks"; 
    prCharWithFreq(str); 
      
# This code is contributed by 'Saloni1297' 

C#

// C# implementation to print the  
// character and its frequency in  
// order of its occurrence 
using System; 
  
class GFG { 
    static int SIZE = 26; 
  
    // function to print the character and its 
    // frequency in order of its occurrence 
    static void printCharWithFreq(String str) 
    { 
        // size of the string 'str' 
        int n = str.Length; 
  
        // 'freq[]' implemented as hash table 
        int[] freq = new int[SIZE]; 
  
        // accumulate freqeuncy of each character 
        // in 'str' 
        for (int i = 0; i < n; i++) 
            freq[str[i] - 'a']++; 
  
        // traverse 'str' from left to right 
        for (int i = 0; i < n; i++) { 
  
            // if frequency of character str.charAt(i) 
            // is not equal to 0 
            if (freq[str[i] - 'a'] != 0) { 
  
                // print the character along with its 
                // frequency 
                Console.Write(str[i]); 
                Console.Write(freq[str[i] - 'a'] + " "); 
  
                // update frequency of str.charAt(i) to 
                // 0 so that the same character is not 
                // printed again 
                freq[str[i] - 'a'] = 0; 
            } 
        } 
    } 
  
    // Driver program to test above 
    public static void Main() 
    { 
        String str = "geeksforgeeks"; 
        printCharWithFreq(str); 
    } 
} 
  
// This code is contributed by Sam007 

PHP

<?php  
// PHP implementation to print the  
// character and its frequency in 
// order of its occurrence 
$SIZE = 26; 
  
// function to print the character and  
// its frequency in order of its occurrence 
function printCharWithFreq($str) 
{ 
    global $SIZE; 
      
    // size of the string 'str' 
    $n = strlen($str); 
  
    // 'freq[]' implemented as hash table 
    $freq = array_fill(0, $SIZE, NULL); 
  
    // accumulate freqeuncy of each  
    // character in 'str' 
    for ($i = 0; $i < $n; $i++) 
        $freq[ord($str[$i]) - ord('a')]++; 
  
    // traverse 'str' from left to right 
    for ($i = 0; $i < $n; $i++)  
    { 
  
        // if frequency of character str[i]  
        // is not equal to 0 
        if ($freq[ord($str[$i]) - ord('a')] != 0)  
        { 
  
            // print the character along with  
            // its frequency 
            echo $str[$i] . $freq[ord($str[$i]) -  
                                  ord('a')] . " "; 
  
            // update frequency of str[i] to 0  
            // so that the same character is  
            // not printed again 
            $freq[ord($str[$i]) - ord('a')] = 0; 
        } 
    } 
} 
  
// Driver Code 
$str = "geeksforgeeks"; 
printCharWithFreq($str); 
  
// This code is contributed by ita_c 
?> 

Output:

g2 e4 k2 s2 f1 o1 r1

Output:

g2 e4 k2 s2 f1 o1 r1

Time Complexity: O(n), where n is the number of characters in the string.
Auxiliary Space: O(1), as there are only lowercase letters.

Alternate Solution (Use Hashing)
We can also use hashing to solve the problem.

# Python3 implementation to print the characters and 
# frequencies in order of its occurrence 
  
def prCharWithFreq(str): 
  
    # Store all characters and their frequencies 
    # in dictionary 
    d = {} 
    for i in str: 
        if i in d: 
            d[i] += 1
        else: 
            d[i] = 1
      
    # Print characters and their frequencies in 
    # same order of their appearance 
    for i in str: 
  
        # Print only if this character is not printed 
        # before.   
        if d[i] != 0: 
            print("{}{}".format(i,d[i]), end =" ") 
            d[i] = 0
       
      
# Driver Code 
if __name__ == "__main__" : 
      
    str = "geeksforgeeks"; 
    prCharWithFreq(str); 
      
# This code is contributed by 'Ankur Tripathi' 

Output:

g2 e4 k2 s2 f1 o1 r1

This article is contributed by Ayush Jauhari. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

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My Personal Notes

Recommended: Please try your approach on {IDE} first, before moving on to the solution.

C++

Java

Python3

C#

PHP

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