Check if two Strings are Anagrams of each other

Try it on GfG Practice

Given two strings s1 and s2 consisting of lowercase characters, the task is to check whether the two given strings are anagrams of each other or not. An anagram of a string is another string that contains the same characters, only the order of characters can be different.

Examples:

Input: s1 = “geeks”  s2 = “kseeg”
Output: true
Explanation: Both the string have same characters with same frequency. So, they are anagrams.

Input: s1 = “allergy”  s2 = “allergic”
Output: false
Explanation: Characters in both the strings are not same. s1 has extra character 'y' and s2 has extra characters 'i' and 'c', so they are not anagrams.

Input: s1 = "g", s2 = "g"
Output: true
Explanation: Characters in both the strings are same, so they are anagrams.

[Naive Approach] Using Sorting

The idea is that if the strings are anagrams, then their characters will be the same, just rearranged. Therefore, if we sort the characters in both strings, the sorted strings will be identical if the original strings were anagrams. We can simply sort the two given strings and compare them – if they are equal, then the original strings are anagrams of each other.

// C++ Code to check if two Strings are anagrams of 
// each other using sorting

#include <algorithm>
#include <iostream>
using namespace std;

// Function to check if two strings are anagrams
bool areAnagrams(string &s1, string &s2) {
    
    // Sort both strings
    sort(s1.begin(), s1.end());
    sort(s2.begin(), s2.end());

    // Compare sorted strings
    return s1 == s2;
}

int main() {
    string s1 = "geeks";
    string s2 = "kseeg";
	cout << (areAnagrams(s1, s2) ? "true" : "false") << endl;

    return 0;
}

// C Code to check if two Strings are anagrams of 
// each other using sorting

#include <stdio.h>
#include <string.h>

// Function to compare two characters (used for sorting)
int compare(const void *a, const void *b) {
    return (*(char *)a - *(char *)b);
}

// Function to check if two strings are anagrams
int areAnagrams(char *s1, char *s2) {
    
    // Check if lengths are equal
    if (strlen(s1) != strlen(s2)) {
        return 0; 
    }

    // Sort both strings
    qsort(s1, strlen(s1), sizeof(char), compare);
    qsort(s2, strlen(s2), sizeof(char), compare);

    // Compare sorted strings
    return strcmp(s1, s2) == 0;
}

int main() {
    char s1[] = "geeks";
    char s2[] = "kseeg";
    printf("%s\n", areAnagrams(s1, s2) ? "true" : "false");

    return 0;
}

// Java Code to check if two Strings are anagrams of 
// each other using sorting

import java.util.Arrays;

class GfG {

    // Function to check if two strings are anagrams
    static boolean areAnagrams(String s1, String s2) {
        
        // Sort both strings
        char[] s1Array = s1.toCharArray();
        char[] s2Array = s2.toCharArray();
        Arrays.sort(s1Array);
        Arrays.sort(s2Array);

        // Compare sorted strings
        return Arrays.equals(s1Array, s2Array);
    }

    public static void main(String[] args) {
        String s1 = "geeks";
        String s2 = "kseeg";
        System.out.println(areAnagrams(s1, s2));
    }
}

# Python Code to check if two Strings are anagram of 
# each other using sorting

def areAnagrams(s1, s2):
    
    # Sort both strings
    s1 = sorted(s1)
    s2 = sorted(s2)

    # Compare sorted strings
    return s1 == s2

if __name__ == "__main__":
    s1 = "geeks"
    s2 = "kseeg"
    print("true" if areAnagrams(s1, s2) else "false")

// C# Code to check if two Strings are anagrams of 
// each other using sorting

using System;

class GfG {
  
    // Function to check if two strings are anagrams
    static bool AreAnagrams(string s1, string s2) {
        
        // Sort both strings
        char[] s1Array = s1.ToCharArray();
        char[] s2Array = s2.ToCharArray();
        Array.Sort(s1Array);
        Array.Sort(s2Array);

        // Compare sorted strings
        return new string(s1Array) == new string(s2Array);
    }

    static void Main() {
        string s1 = "geeks";
        string s2 = "kseeg";
        Console.WriteLine(AreAnagrams(s1, s2) ? "true" : "false");
    }
}

// JavaScript Code to check if two Strings are anagram of 
// each other using sorting

function areAnagrams(s1, s2) {
    
    // Sort both strings
    s1 = s1.split('').sort().join('');
    s2 = s2.split('').sort().join('');

    // Compare sorted strings
    return s1 === s2;
}

const s1 = "geeks";
const s2 = "kseeg";
console.log(areAnagrams(s1, s2));

true

Time Complexity: O(m*log(m) + n*log(n)), where m and n are length of string s1 and s2 respectively.
Auxiliary Space: O(1) where the strings are mutable but O(n) in languages like Java, Python, C#, etc. where strings are immutable.

[Expected Approach 1] Using Hash Map or Dictionary

The idea is to use a hash map or dictionary count the frequency of each character in both the input strings. If the frequency of every character matches in both strings, then the strings are anagrams.

• First, count the occurrences of each character in first string.
• Then, decrement the count for each character in the second string.
• If the strings are anagrams, all positions in the frequency array should be zero as any non-zero position means that the frequency of that character is not same in both strings.

// C++ Code to check if two Strings are anagram of 
// each other using Hash map

#include <algorithm>
#include <iostream>
#include <vector>
#include <unordered_map>
using namespace std;

bool areAnagrams(string &s1, string &s2) {
    
    // Create a hashmap to store character frequencies
    unordered_map<char, int> charCount;
    
    // Count frequency of each character in string s1
    for(char ch: s1) 
    	charCount[ch] += 1;
  
    // Count frequency of each character in string s2
    for(char ch: s2) 
    	charCount[ch] -= 1;
  
    // Check if all frequencies are zero
    for (auto& pair : charCount) {
        if (pair.second != 0) {
            return false;
        }
    }
    
    // If all conditions satisfied, they are anagrams
    return true;
}

int main() {
    string s1 = "geeks";
    string s2 = "kseeg";
	cout << (areAnagrams(s1, s2) ? "true" : "false") << endl;

    return 0;
}

// Java Code to check if two Strings are anagram of 
// each other using Hash map

import java.util.HashMap;

class GfG {
    
    static boolean areAnagrams(String s1, String s2) {
        
        // Create a hashmap to store character frequencies
        HashMap<Character, Integer> charCount = new HashMap<>();
        
        // Count frequency of each character in string s1
        for (char ch : s1.toCharArray()) 
            charCount.put(ch, charCount.getOrDefault(ch, 0) + 1);
  
        // Count frequency of each character in string s2
        for (char ch : s2.toCharArray()) 
            charCount.put(ch, charCount.getOrDefault(ch, 0) - 1);
  
        // Check if all frequencies are zero
        for (var pair : charCount.entrySet()) {
            if (pair.getValue() != 0) {
                return false;
            }
        }
        
        // If all conditions satisfied, they are anagrams
        return true;
    }

    public static void main(String[] args) {
        String s1 = "geeks";
        String s2 = "kseeg";
        System.out.println(areAnagrams(s1, s2) ? "true" : "false");
    }
}

# Python Code to check if two Strings are anagram of 
# each other using Dictionary

def areAnagrams(s1, s2):
    
    # Create a hashmap to store character frequencies
    charCount = {}
    
    # Count frequency of each character in string s1
    for ch in s1:
        charCount[ch] = charCount.get(ch, 0) + 1
  
    # Count frequency of each character in string s2
    for ch in s2:
        charCount[ch] = charCount.get(ch, 0) - 1
  
    # Check if all frequencies are zero
    for value in charCount.values():
        if value != 0:
            return False
    
    # If all conditions satisfied, they are anagrams
    return True

if __name__ == "__main__":
    s1 = "geeks"
    s2 = "kseeg"
    print("true" if areAnagrams(s1, s2) else "false")

// C# Code to check if two Strings are anagram of 
// each other using Dictionary

using System;
using System.Collections.Generic;

class GfG {
    static bool areAnagrams(string s1, string s2) {
      
        // Create a dictionary to store character frequencies
        Dictionary<char, int> charCount = new Dictionary<char, int>();
        
        // Count frequency of each character in string s1
        foreach (char ch in s1) 
            charCount[ch] = charCount.GetValueOrDefault(ch, 0) + 1;

        // Count frequency of each character in string s2
        foreach (char ch in s2) 
            charCount[ch] = charCount.GetValueOrDefault(ch, 0) - 1;

        // Check if all frequencies are zero
        foreach (var pair in charCount) {
            if (pair.Value != 0) 
                return false;
        }
        
        // If all conditions satisfied, they are anagrams
        return true;
    }

    static void Main(string[] args) {
        string s1 = "geeks";
        string s2 = "kseeg";
        Console.WriteLine(areAnagrams(s1, s2) ? "true" : "false");
    }
}

// JavaScript Code to check if two Strings are anagram of 
// each other using Hash map

function areAnagrams(s1, s2) {
    
    // Create a hashmap to store character frequencies
    const charCount = {};
    
    // Count frequency of each character in string s1
    for (let ch of s1) 
        charCount[ch] = (charCount[ch] || 0) + 1;

    // Count frequency of each character in string s2
    for (let ch of s2) 
        charCount[ch] = (charCount[ch] || 0) - 1;

    // Check if all frequencies are zero
    for (let key in charCount) {
        if (charCount[key] !== 0) {
            return false;
        }
    }
    
    // If all conditions satisfied, they are anagrams
    return true;
}

const s1 = "geeks";
const s2 = "kseeg";
console.log(areAnagrams(s1, s2) ? "true" : "false");

true

Time Complexity: O(m + n), where m and n are length of string s1 and s2 respectively.
Auxiliary Space: O(26) = O(1). The input strings can only have lowercase letters, so there can be at most 26 distinct characters in the hash map.

[Expected Approach 2] Using Frequency Array

Instead of using a hash map to store the frequency of each character, we can create a frequency array of size 26 by using characters as index in this array. The frequency of ‘a’ is going to be stored at index 0, ‘b’ at 1, and so on. To find the index of a character, we subtract character a’s ASCII value from the ASCII value of the character.

Count character frequency in the first string, then for each character in the second string, decrement its count from the frequency array. If the strings are anagrams, all positions in the frequency array will be zero. Any non-zero position means the frequency of that character is not equal in both the strings.

Working:

// C++ Code to check if two Strings are anagram of 
// each other using Frequency Array

#include <algorithm>
#include <iostream>
#include <vector>
using namespace std;

// As the input strings can only have lowercase 
// characters, the maximum characters will be 26
const int MAX_CHAR = 26;

bool areAnagrams(string &s1, string &s2) {
    vector<int> freq(MAX_CHAR, 0);
    
    // Count frequency of each character in string s1
    for(char ch: s1) 
    	freq[ch - 'a']++;
  
    // Count frequency of each character in string s2
    for(char ch: s2) 
    	freq[ch - 'a']--;
  
    // Check if all frequencies are zero
    for (int count : freq) {
        if (count != 0) 
            return false;
    }
    
    return true;
}

int main() {
    string s1 = "geeks";
    string s2 = "kseeg";
	cout << (areAnagrams(s1, s2) ? "true" : "false") << endl;

    return 0;
}

// C Code to check if two Strings are anagram of 
// each other using Frequency Array

#include <stdio.h>
#include <string.h>
#include <stdbool.h>

// As the input strings can only have lowercase characters
#define MAX_CHAR 26 

int areAnagrams(char *s1, char *s2) {
    int freq[MAX_CHAR] = {0};

    // Count frequency of each character in string s1
    for (int i = 0; s1[i] != '\0'; i++) 
        freq[s1[i] - 'a']++;

    // Count frequency of each character in string s2
    for (int i = 0; s2[i] != '\0'; i++)
        freq[s2[i] - 'a']--;

    // Check if all frequencies are zero
    for (int i = 0; i < MAX_CHAR; i++) {
        if (freq[i] != 0) {
            return false;
        }
    }

    return true;
}

int main() {
    char s1[] = "geeks";
    char s2[] = "kseeg";
    printf("%s\n", areAnagrams(s1, s2) ? "true" : "false");

    return 0;
}

// Java Code to check if two Strings are anagram of 
// each other using Frequency Array

class GfG {

    // As the input strings can only have lowercase 
    // characters, the maximum characters will be 26
    static final int MAX_CHAR = 26;

    static boolean areAnagrams(String s1, String s2) {
        int[] freq = new int[MAX_CHAR];

        // Count frequency of each character in string s1
        for (int i = 0; i < s1.length(); i++)
            freq[s1.charAt(i) - 'a']++;

        // Count frequency of each character in string s2
        for (int i = 0; i < s2.length(); i++)
            freq[s2.charAt(i) - 'a']--;

        // Check if all frequencies are zero
        for (int count : freq) {
            if (count != 0)
                return false;
        }

        return true;
    }

    public static void main(String[] args) {
        String s1 = "geeks";
        String s2 = "kseeg";
        System.out.println(areAnagrams(s1, s2));
    }
}

# Python Code to check if two Strings are anagram of 
# each other using Frequency Array

# As the input strings can only have lowercase 
# characters, the maximum characters will be 26
MAX_CHAR = 26

def areAnagrams(s1, s2):
    freq = [0] * MAX_CHAR
    
    # Count frequency of each character in string s1
    for ch in s1:
        freq[ord(ch) - ord('a')] += 1

    # Count frequency of each character in string s2
    for ch in s2:
        freq[ord(ch) - ord('a')] -= 1

    # Check if all frequencies are zero
    for count in freq:
        if count != 0:
            return False
            
    return True

if __name__ == "__main__":
    s1 = "geeks"
    s2 = "kseeg"
    print("true" if areAnagrams(s1, s2) else "false")

// C# Code to check if two Strings are anagram of 
// each other using Frequency Array

using System;

class GfG {
  
    // As the input strings can only have lowercase 
    // characters, the maximum characters will be 26
    const int MAX_CHAR = 26;

    static bool AreAnagrams(string s1, string s2) {
        int[] freq = new int[MAX_CHAR];

        // Count frequency of each character in string s1
        foreach (char ch in s1)
            freq[ch - 'a']++;

        // Count frequency of each character in string s2
        foreach (char ch in s2)
            freq[ch - 'a']--;

        // Check if all frequencies are zero
        foreach (int count in freq) {
            if (count != 0)
                return false;
        }

        return true;
    }

    static void Main() {
        string s1 = "geeks";
        string s2 = "kseeg";
        Console.WriteLine(AreAnagrams(s1, s2) ? "true" : "false");
    }
}

// JavaScript Code to check if two Strings are anagram of 
// each other using Frequency Array

// As the input strings can only have lowercase 
// characters, the maximum characters will be 26
const MAX_CHAR = 26;

function areAnagrams(s1, s2) {
    let freq = new Array(MAX_CHAR).fill(0);
    
    // Count frequency of each character in string s1
    for (let ch of s1) 
        freq[ch.charCodeAt(0) - 'a'.charCodeAt(0)]++;
  
    // Count frequency of each character in string s2
    for (let ch of s2) 
        freq[ch.charCodeAt(0) - 'a'.charCodeAt(0)]--;
  
    // Check if all frequencies are zero
    for (let count of freq) {
        if (count !== 0) 
            return false;
    }
    
    return true;
}

const s1 = "geeks";
const s2 = "kseeg";
console.log(areAnagrams(s1, s2) ? "true" : "false");

true

Time Complexity: O(m + n), where m and n are length of string s1 and s2 respectively.
Auxiliary Space: O(MAX_CHAR) = O(26) = O(1), the input strings can only have lowercase letters, so we only need frequency array of size 26.

kartik

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