Print characters having odd frequencies in order of occurrence

12 May, 2021
Given a string str containing only lowercase characters. The task is to print the characters having an odd frequency in the order of their occurrence.Note: Repeated elements with odd frequency are printed as many times they occur in order of their occurrences.Examples: 
Input: str = “geeksforgeeks” Output: for  
‘f’, ‘o’ and ‘r’ are the only characters with odd frequencies.Input: str = “elephant” Output: lphant 
Approach: Create a frequency array to store the frequency of each of the characters of the given string str. Traverse the string str again and check whether the frequency of that character is odd. If yes, then print the character.Below is the implementation of the above approach: 
C++
Java
Python3
C#
Javascript
// C++ implementation of the approach#include <bits/stdc++.h>using namespace std;#define SIZE 26 // Function to print the odd frequency characters// in the order of their occurrencevoid printChar(string str, int n){     // To store the frequency of each of    // the character of the string    int freq[SIZE];     // Initialize all elements of freq[] to 0    memset(freq, 0, sizeof(freq));     // Update the frequency of each character    for (int i = 0; i < n; i++)        freq[str[i] - 'a']++;     // Traverse str character by character    for (int i = 0; i < n; i++) {         // If frequency of current character is odd        if (freq[str[i] - 'a'] % 2 == 1) {            cout << str[i];        }    }} // Driver codeint main(){    string str = "geeksforgeeks";    int n = str.length();    printChar(str, n);     return 0;}
// Java implementation of the approachclass GFG {    // Function to print the odd frequency characters    // in the order of their occurrence    public static void printChar(String str, int n)    {         // To store the frequency of each of        // the character of the string        int[] freq = new int[26];         // Update the frequency of each character        for (int i = 0; i < n; i++)            freq[str.charAt(i) - 'a']++;         // Traverse str character by character        for (int i = 0; i < n; i++) {             // If frequency of current character is odd            if (freq[str.charAt(i) - 'a'] % 2 == 1) {                System.out.print(str.charAt(i));            }        }    }     // Driver code    public static void main(String[] args)    {        String str = "geeksforgeeks";        int n = str.length();        printChar(str, n);    }} // This code is contributed by Naman_Garg.
# Python3 implementation of the approachimport sysimport math # Function to print the odd frequency characters# in the order of their occurrencedef printChar(str_, n):     # To store the frequency of each of    # the character of the string and    # Initialize all elements of freq[] to 0    freq = [0] * 26     # Update the frequency of each character    for i in range(n):        freq[ord(str_[i]) - ord('a')] += 1         # Traverse str character by character    for i in range(n):         # If frequency of current character is odd        if (freq[ord(str_[i]) -                 ord('a')]) % 2 == 1:            print("{}".format(str_[i]), end = "") # Driver codeif __name__=='__main__':    str_ = "geeksforgeeks"    n = len(str_)    printChar(str_, n) # This code is contributed by Vikash Kumar 37
// C# implementation of the approachusing System; class GFG {    // Function to print the odd frequency characters    // in the order of their occurrence    public static void printChar(String str, int n)    {         // To store the frequency of each of        // the character of the string        int[] freq = new int[26];         // Update the frequency of each character        for (int i = 0; i < n; i++)            freq[str[i] - 'a']++;         // Traverse str character by character        for (int i = 0; i < n; i++) {             // If frequency of current character is odd            if (freq[str[i] - 'a'] % 2 == 1) {                Console.Write(str[i]);            }        }    }     // Driver code    public static void Main(String[] args)    {        String str = "geeksforgeeks";        int n = str.Length;        printChar(str, n);    }} // This code has been contributed by 29AjayKumar
<script>// javascript implementation of the approach let SIZE = 26; // Function to print the odd frequency characters// in the order of their occurrencefunction printChar(str, n){    // To store the frequency of each of    // the character of the string    let freq = [];     // Initialize all elements of freq[] to 0    for(let i = 0; i < SIZE; i++){        freq.push(0);    }     // Update the frequency of each character    for (let i = 0; i < n; i++)        freq[str.charCodeAt(i) - 97]++;     // Traverse str character by character    for (let i = 0; i < n; i++) {         // If frequency of current character is odd        if (freq[str.charCodeAt(i) - 97] % 2 == 1) {            document.write(str[i]);        }    }} let str = "geeksforgeeks";let n = str.length;printChar(str, n); // This code is contributed by rohitsingh07052.</script>
Output: 
for
Time Complexity: O(n) Auxiliary Space: O(1) 
Approach:
We will scan the string and count the occurrence of all characters  using built in Counter() function after that we  traverse the counter list and check if the occurrences are odd or not  if there is any even frequency character then we immediately print No.
Note: This method is applicable for all type of characters
Below is the implementation of the above approach:
Python3
# importing Counter functionfrom collections import Counter # function to check if all# elements occur odd timesdef checkString(s):       # Counting the frequency of all    # character using Counter function    frequency = Counter(s)         # Traversing frequency    for i in frequency:               # Checking if any element        # has even count        if (frequency[i] % 2 == 0):            return False    return True  # Driver codes = "gggfffaaa"if(checkString(s)):    print("Yes")else:    print("No")     # This code is contributed by vikkycirus
Output:
Yes
Vikash Kumar 37
Naman_Garg
29AjayKumar
vikkycirus
rohitsingh07052
frequency-counting
Arrays
Hash
Strings
Arrays
Hash
Strings
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