Print characters and their frequencies in order of occurrence - GeeksforGeeks

09 Feb, 2022
Given 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
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++
Java
Python3
C#
PHP
Javascript
// 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 occurrencevoid 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 frequency 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 aboveint main(){    string str = "geeksforgeeks";    printCharWithFreq(str);    return 0;}
// Java implementation to print the character and// its frequency in order of its occurrencepublic 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 frequency 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 implementation to pr the character and# its frequency in order of its occurrence # import libraryimport numpy as np # Function to print the character and its# frequency in order of its occurrencedef prCharWithFreq(str) :         # Size of the 'str'    n = len(str)         # Initialize all elements of freq[] to 0    freq = np.zeros(26, dtype = np.int)     # Accumulate frequency 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 Codeif __name__ == "__main__" :         str = "geeksforgeeks";    prCharWithFreq(str);     # This code is contributed by 'Saloni1297'
// C# implementation to print the// character and its frequency in// order of its occurrenceusing 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 frequency 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 implementation to print the// character and its frequency in// order of its occurrence$SIZE = 26; // function to print the character and// its frequency in order of its occurrencefunction printCharWithFreq($str){    global $SIZE;         // size of the string 'str'    $n = strlen($str);     // 'freq[]' implemented as hash table    $freq = array_fill(0, $SIZE, NULL);     // accumulate frequency of each    // character in 'str'    for ($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?>
<script>// Javascript implementation to print the character and// its frequency in order of its occurrence         let SIZE = 26;         // function to print the character and its    // frequency in order of its occurrence    function printCharWithFreq(str)    {             // size of the string 'str'        let n = str.length;          // 'freq[]' implemented as hash table        let freq = new Array(SIZE);        for(let i = 0; i < freq.length; i++)        {            freq[i] = 0;        }          // accumulate frequency of each character        // in 'str'        for (let i = 0; i < n; i++)            freq[str[i].charCodeAt(0) - 'a'.charCodeAt(0)]++;          // traverse 'str' from left to right        for (let i = 0; i < n; i++) {              // if frequency of character str.charAt(i)            // is not equal to 0            if (freq[str[i].charCodeAt(0) - 'a'.charCodeAt(0)] != 0) {                  // print the character along with its                // frequency                document.write(str[i]);                document.write(freq[str[i].charCodeAt(0) - 'a'.charCodeAt(0)] + " ");                  // update frequency of str.charAt(i) to                // 0 so that the same character is not                // printed again                freq[str[i].charCodeAt(0) - 'a'.charCodeAt(0)] = 0;            }        }    }         // Driver program to test above    let str = "geeksforgeeks";    printCharWithFreq(str);         // This code is contributed by rag2127.     </script>
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. 
C++
Java
Python3
C#
Javascript
// C++ implementation to//print the characters and// frequencies in order// of its occurrence#include <bits/stdc++.h>using namespace std; void prCharWithFreq(string s){  // Store all characters and  // their frequencies in dictionary  unordered_map<char, int> d;   for(char i : s)  {    d[i]++;  }   // Print characters and their  // frequencies in same order  // of their appearance  for(char i : s)  {    // Print only if this    // character is not printed    // before    if(d[i] != 0)    {      cout << i << d[i] << " ";      d[i] = 0;    }  }}  // Driver Codeint main(){  string s="geeksforgeeks";  prCharWithFreq(s);} // This code is contributed by rutvik_56
// Java implementation to// print the characters and// frequencies in order// of its occurrenceimport java.util.*;class Gfg{    public static void prCharWithFreq(String s)    {               // Store all characters and        // their frequencies in dictionary        Map<Character, Integer> d = new HashMap<Character, Integer>();                          for(int i = 0; i < s.length(); i++)        {            if(d.containsKey(s.charAt(i)))            {                d.put(s.charAt(i), d.get(s.charAt(i)) + 1);            }            else            {                d.put(s.charAt(i), 1);            }        }                 // Print characters and their        // frequencies in same order        // of their appearance        for(int i = 0; i < s.length(); i++)        {                       // Print only if this            // character is not printed            // before            if(d.get(s.charAt(i)) != 0)            {                System.out.print(s.charAt(i));                System.out.print(d.get(s.charAt(i)) + " ");                d.put(s.charAt(i), 0);            }                   }    }       // Driver code     public static void main(String []args)     {       String S = "geeksforgeeks";       prCharWithFreq(S);     }} // This code is contributed by avanitrachhadiya2155
# 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 Codeif __name__ == "__main__" :         str = "geeksforgeeks";    prCharWithFreq(str);     # This code is contributed by 'Ankur Tripathi'
// C# implementation to// print the characters and// frequencies in order// of its occurrence using System;using System.Collections;using System.Collections.Generic; class GFG{     public static void prCharWithFreq(string s){     // Store all characters and  // their frequencies in dictionary  Dictionary<char,int> d = new Dictionary<char,int>();    foreach(char i in s)  {      if(d.ContainsKey(i))      {        d[i]++;      }      else      {        d[i]=1;       }  }    // Print characters and their  // frequencies in same order  // of their appearance  foreach(char i in s)  {    // Print only if this    // character is not printed    // before    if(d[i] != 0)    {        Console.Write(i+d[i].ToString() + " ");        d[i] = 0;    }  }}   // Driver Codepublic static void Main(string []args){  string s="geeksforgeeks";  prCharWithFreq(s);}} // This code is contributed by pratham76
<script>// Javascript implementation to//print the characters and// frequencies in order// of its occurrence function prCharWithFreq(s){  // Store all characters and  // their frequencies in dictionary  var d = new Map();   s.split('').forEach(element => {             if(d.has(element))        {            d.set(element, d.get(element)+1);        }        else            d.set(element, 1);  });   // Print characters and their  // frequencies in same order  // of their appearance   s.split('').forEach(element => {    // Print only if this    // character is not printed    // before    if(d.has(element) && d.get(element)!=0)    {      document.write( element + d.get(element) + " ");      d.set(element, 0);    }  });}  // Driver Codevar s="geeksforgeeks";prCharWithFreq(s); </script>
g2 e4 k2 s2 f1 o1 r1 
We can solve this problem quickly using the python Counter() method. The approach is very simple.
1) First create a dictionary using the Counter method having strings as keys and their frequencies as values.
2)Traverse in this dictionary print keys along with their values
Python3
# Python3 implementation to print the characters and# frequencies in order of its occurrencefrom collections import Counter def prCharWithFreq(string):     # Store all characters and their    # frequencies using Counter function    d = Counter(string)     # Print characters and their frequencies in    # same order of their appearance    for i in d:        print(i+str(d[i]), end=" ")  string = "geeksforgeeks"prCharWithFreq(string) # This code is contributed by vikkycirus
g2 e4 k2 s2 f1 o1 r1 
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pratham76
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