Check if both halves of the string have same set of characters

Given a string of lowercase characters only, the task is to check if it is possible to split a string from middle which will gives two halves having the same characters and same frequency of each character. If the length of the given string is ODD then ignore the middle element and check for the rest.

Examples:

Input : abbaab
Output : NO
The two halves contain the same characters
but their frequencies do not match so they
are NOT CORRECT

Input : abccab
Output : YES

Algorithm:

Declare two counter arrays for keeping count of characters in two half of the string, each of size 26.
Now run a loop and take two variables i and j, where i starts from 0 and j starts from (length of string – 1).
For each character in the string, go to the corresponding index in the counter arrays and increment the value by 1 and increment i and decrement j. Do this until i is less than j.
After finishing STEP 3, again run a loop and compare values of counter arrays. If value of first array if not equal to value of second array, then return false.
If all counts matched, return true.

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

Below is the implementation of above idea:

C++

// C++ program to check if it is 
// possible to split string or not 
#include <bits/stdc++.h> 
using namespace std; 
const int MAX_CHAR = 26; 
  
// function to check if we can spilt 
// string or not 
bool checkCorrectOrNot(string s) 
{ 
    // Counter array inisialized with 0 
    int count1[MAX_CHAR] = {0}; 
    int count2[MAX_CHAR] = {0}; 
  
    // Length of the string 
    int n = s.length(); 
    if (n == 1) 
        return true; 
  
    // traverse till the middle element 
    // is reached 
    for (int i=0,j=n-1; i<j; i++,j--) 
    { 
        // First half 
        count1[s[i]-'a']++; 
  
        // Second half 
        count2[s[j]-'a']++; 
    } 
  
    // Checking if values are diffrent 
    // set flag to 1 
    for (int i = 0; i<MAX_CHAR; i++) 
        if (count1[i] != count2[i]) 
            return false; 
  
    return true; 
} 
  
// Driver program to test above function 
int main() 
{ 
    // String to be checked 
    string s = "abab"; 
  
    if (checkCorrectOrNot(s)) 
        cout << "Yes\n"; 
    else
        cout << "No\n"; 
    return 0; 
} 

Java

// Java program to check if it two  
// half of string contain same Character 
// set or not 
public class GFG { 
  
    static final int MAX_CHAR = 26; 
       
    // function to check both halves 
    // for equality 
    static boolean checkCorrectOrNot(String s) 
    { 
        // Counter array inisialized with 0 
        int[] count1 = new int[MAX_CHAR]; 
        int[] count2 = new int[MAX_CHAR]; 
       
        // Length of the string 
        int n = s.length(); 
        if (n == 1) 
            return true; 
       
        // traverse till the middle element 
        // is reached 
        for (int i = 0, j = n - 1; i < j; i++, j--) 
        { 
            // First half 
            count1[s.charAt(i) - 'a']++; 
       
            // Second half 
            count2[s.charAt(j) - 'a']++; 
        } 
       
        // Checking if values are different 
        // set flag to 1 
        for (int i = 0; i < MAX_CHAR; i++) 
            if (count1[i] != count2[i]) 
                return false; 
       
        return true; 
    } 
       
    // Driver program to test above function 
    public static void main(String args[]) 
    { 
        // String to be checked 
        String s = "abab"; 
       
        if (checkCorrectOrNot(s)) 
            System.out.println("Yes"); 
        else
            System.out.println("No"); 
    } 
} 
// This code is contributed by Sumit Ghosh 

Python3

# Python3 program to check if it is 
# possible to split string or not 
MAX_CHAR = 26
  
# Function to check if we  
# can spilt string or not 
def checkCorrectOrNot(s): 
      
    global MAX_CHAR 
      
    # Counter array inisialized with 0 
    count1 = [0] * MAX_CHAR 
    count2 = [0] * MAX_CHAR 
  
    # Length of the string 
    n = len(s) 
      
    if n == 1: 
        return true 
  
    # Traverse till the middle  
    # element is reached 
    i = 0; j = n - 1
      
    while (i < j): 
          
        # First half 
        count1[ord(s[i]) - ord('a')] += 1
  
        # Second half 
        count2[ord(s[j]) - ord('a')] += 1
  
        i += 1; j -= 1
  
    # Checking if values are  
    # diffrent set flag to 1 
    for i in range(MAX_CHAR): 
          
        if count1[i] != count2[i]: 
            return False
              
    return True
  
  
# Driver Code 
  
# String to be checked 
s = "ababc"
  
print("Yes" if checkCorrectOrNot(s) else "No") 
  
  
# This code is contributed by Ansu Kumari. 

C#

// C# program to check if it two half of  
// string contain same Character set or not 
using System; 
  
class GFG { 
  
    static int MAX_CHAR = 26; 
      
    // function to check both halves for  
    // equality 
    static bool checkCorrectOrNot(string s) 
    { 
          
        // Counter array inisialized with 0 
        int []count1 = new int[MAX_CHAR]; 
        int []count2 = new int[MAX_CHAR]; 
      
        // Length of the string 
        int n = s.Length; 
        if (n == 1) 
            return true; 
      
        // traverse till the middle element 
        // is reached 
        for (int i = 0, j = n - 1; i < j; 
                                   i++, j--) 
        { 
              
            // First half 
            count1[s[i] - 'a']++; 
      
            // Second half 
            count2[s[j] - 'a']++; 
        } 
      
        // Checking if values are different 
        // set flag to 1 
        for (int i = 0; i < MAX_CHAR; i++) 
            if (count1[i] != count2[i]) 
                return false; 
      
        return true; 
    } 
      
    // Driver program to test above function 
    public static void Main() 
    { 
        // String to be checked 
        string s = "abab"; 
      
        if (checkCorrectOrNot(s)) 
            Console.Write("Yes"); 
        else
            Console.Write("No"); 
    } 
} 
  
// This code is contributed by nitin mittal 

PHP

<?php  
// PHP program to check if it is 
// possible to split string or not 
$MAX_CHAR = 26; 
  
// function to check if we  
// can spilt string or not 
function checkCorrectOrNot($s) 
{ 
    global $MAX_CHAR; 
      
    // Counter array inisialized with 0 
    $count1 = array_fill(0, $MAX_CHAR, NULL); 
    $count2 = array_fill(0, $MAX_CHAR, NULL); 
  
    // Length of the string 
    $n = strlen($s); 
    if ($n == 1) 
        return true; 
  
    // traverse till the middle  
    // element is reached 
    for ($i = 0, $j = $n - 1;  
         $i < $j; $i++, $j--) 
    { 
        // First half 
        $count1[$s[$i] - 'a']++; 
  
        // Second half 
        $count2[$s[$j] - 'a']++; 
    } 
  
    // Checking if values are  
    // diffrent set flag to 1 
    for ($i = 0; $i < $MAX_CHAR; $i++) 
        if ($count1[$i] != $count2[$i]) 
            return false; 
  
    return true; 
} 
  
// Driver Code 
  
// String to be checked 
$s = "abab"; 
if (checkCorrectOrNot($s)) 
    echo "Yes\n"; 
else
    echo "No\n"; 
  
// This code is contributed  
// by ChitraNayal 
?> 

Output :

YES

Space optimized solution:
Below is the space optimized solution of the above approach.

We can solve this problem by using only 1 counter array.
Take a string and increment counts for first half and then decrement counts for second half.
If final counter array is 0, then return true, Else False.

Below is the implementation of above idea:

C++

// C++ program to check if it is 
// possible to split string or not 
#include <bits/stdc++.h> 
using namespace std; 
const int MAX_CHAR = 26; 
  
// function to check if we can spilt 
// string or not 
bool checkCorrectOrNot(string s) 
{ 
    // Counter array inisialized with 0 
    int count[MAX_CHAR] = {0}; 
  
    // Length of the string 
    int n = s.length(); 
    if (n == 1) 
        return true; 
  
    // traverse till the middle element 
    // is reached 
    for (int i=0,j=n-1; i<j; i++,j--) 
    { 
        // First half 
        count[s[i]-'a']++; 
  
        // Second half 
        count[s[j]-'a']--; 
    } 
  
    // Checking if values are diffrent 
    // set flag to 1 
    for (int i = 0; i<MAX_CHAR; i++) 
        if (count[i] != 0) 
            return false; 
  
    return true; 
} 
  
// Driver program to test above function 
int main() 
{ 
    // String to be checked 
    string s = "abab"; 
  
    if (checkCorrectOrNot(s)) 
        cout << "Yes\n"; 
    else
        cout << "No\n"; 
    return 0; 
} 

Java

// Java program to check if it two  
// half of string contain same Character 
// set or not 
public class GFG { 
  
    static final int MAX_CHAR = 26; 
       
    // function to check both halves 
    // for equality 
    static boolean checkCorrectOrNot(String s) 
    { 
        // Counter array inisialized with 0 
        int[] count = new int[MAX_CHAR]; 
       
        // Length of the string 
        int n = s.length(); 
        if (n == 1) 
            return true; 
       
        // traverse till the middle element 
        // is reached 
        for (int i = 0,j = n - 1; i < j; i++, j--) 
        { 
            // First half 
            count[s.charAt(i) - 'a']++; 
       
            // Second half 
            count[s.charAt(j) - 'a']--; 
        } 
       
        // Checking if values are different 
        // set flag to 1 
        for (int i = 0; i < MAX_CHAR; i++) 
            if (count[i] != 0) 
                return false; 
       
        return true; 
    } 
       
    // Driver program to test above function 
    public static void main(String args[]) 
    { 
        // String to be checked 
        String s = "abab"; 
       
        if (checkCorrectOrNot(s)) 
            System.out.println("Yes"); 
        else
           System.out.println("No"); 
    } 
} 
// This code is contributed by Sumit Ghosh 

Python3

# Python3 program to check if it is 
# possible to split string or not 
MAX_CHAR = 26
  
# Function to check if we   
# can spilt string or not 
def checkCorrectOrNot(s): 
      
    global MAX_CHAR 
      
    # Counter array inisialized with 0 
    count = [0] * MAX_CHAR 
  
    # Length of the string 
    n = len(s) 
      
    if n == 1: 
        return true 
  
    # Traverse till the middle  
    # element is reached 
    i = 0; j = n-1
      
    while i < j: 
          
        # First half 
        count[ord(s[i]) - ord('a')] += 1
  
        # Second half 
        count[ord(s[j])-ord('a')] -= 1
  
        i += 1; j -= 1
  
    # Checking if values are  
    # diffrent, set flag to 1 
    for i in range(MAX_CHAR): 
          
        if count[i] != 0: 
            return False
  
    return True
  
  
# Driver Code 
  
# String to be checked 
s = "abab"
  
print("Yes" if checkCorrectOrNot(s) else "No") 
  
  
# This code is contributed by Ansu Kumari. 

C#

// C# program to check if it two  
// half of string contain same Character 
// set or not 
using System; 
  
public class GFG { 
  
    static int MAX_CHAR = 26; 
      
    // function to check both halves 
    // for equality 
    static bool checkCorrectOrNot(String s) 
    { 
          
        // Counter array inisialized with 0 
        int[] count = new int[MAX_CHAR]; 
      
        // Length of the string 
        int n = s.Length; 
        if (n == 1) 
            return true; 
      
        // traverse till the middle element 
        // is reached 
        for (int i = 0, j = n - 1; i < j; i++, j--) 
        { 
            // First half 
            count[s[i] - 'a']++; 
      
            // Second half 
            count[s[j] - 'a']--; 
        } 
      
        // Checking if values are different 
        // set flag to 1 
        for (int i = 0; i < MAX_CHAR; i++) 
            if (count[i] != 0) 
                return false; 
      
        return true; 
    } 
      
    // Driver program to test above function 
    public static void Main(String []args) 
    { 
          
        // String to be checked 
        String s = "abab"; 
      
        if (checkCorrectOrNot(s)) 
            Console.Write("Yes"); 
        else
            Console.Write("No"); 
    } 
} 
  
// This code is contributed by parashar. 

PHP

<?PHP  
// PHP program to check if it is 
// possible to split string or not 
$MAX_CHAR = 26; 
  
// function to check if we  
// can spilt string or not 
function checkCorrectOrNot($s) 
{ 
    global $MAX_CHAR; 
      
    // Counter array inisialized with 0 
    $count = array_fill(0, $MAX_CHAR, NULL); 
  
    // Length of the string 
    $n = strlen($s); 
    if ($n == 1) 
        return true; 
  
    // traverse till the middle  
    // element is reached 
    for ($i = 0, $j = $n - 1;  
         $i < $j; $i++, $j--) 
    { 
        // First half 
        $count[$s[$i] - 'a']++; 
  
        // Second half 
        $count[$s[$j] - 'a']--; 
    } 
  
    // Checking if values are  
    // diffrent set flag to 1 
    for ($i = 0; $i < $MAX_CHAR; $i++) 
        if ($count[$i] != 0) 
            return false; 
  
    return true; 
} 
  
// Driver Code 
  
// String to be checked 
$s = "abab"; 
if (checkCorrectOrNot($s)) 
    echo "Yes\n"; 
else
    echo "No\n"; 
  
// This code is contributed  
// by ChitraNayal 
?> 

Output:

YES

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