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

26 May, 2022
Given a string of lowercase characters only, the task is to check if it is possible to split a string from the middle which will give 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.
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.
Below is the implementation of above idea: 
C++
Java
Python3
C#
PHP
Javascript
// 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 split// string or notbool checkCorrectOrNot(string s){    // Counter array initialized 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 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 functionint main(){    // String to be checked    string s = "abab";     if (checkCorrectOrNot(s))        cout << "Yes\n";    else        cout << "No\n";    return 0;}
// Java program to check if it two// half of string contain same Character// set or notpublic class GFG {     static final int MAX_CHAR = 26;          // function to check both halves    // for equality    static boolean checkCorrectOrNot(String s)    {        // Counter array initialized 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 program to check if it is# possible to split string or notMAX_CHAR = 26 # Function to check if we# can split string or notdef checkCorrectOrNot(s):         global MAX_CHAR         # Counter array initialized 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    # different set flag to 1    for i in range(MAX_CHAR):                 if count1[i] != count2[i]:            return False                 return True  # Driver Code # String to be checkeds = "ababc" print("Yes" if checkCorrectOrNot(s) else "No")  # This code is contributed by Ansu Kumari.
// C# program to check if it two half of// string contain same Character set or notusing System; class GFG {     static int MAX_CHAR = 26;         // function to check both halves for    // equality    static bool checkCorrectOrNot(string s)    {                 // Counter array initialized 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 program to check if it is// possible to split string or not$MAX_CHAR = 26; // function to check if we// can split string or notfunction checkCorrectOrNot($s){    global $MAX_CHAR;         // Counter array initialized 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[$j] - 'a']++;    }     // Checking if values are    // different set flag to 1    for ($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?>
<script>// Javascript program to check if it two// half of string contain same Character// set or not         let MAX_CHAR = 26;         // function to check both halves    // for equality    function checkCorrectOrNot(s)    {        // Counter array initialized with 0        let count1 = new Array(MAX_CHAR);        let count2 = new Array(MAX_CHAR);        for(let i=0;i<MAX_CHAR;i++)        {            count1[i]=0;            count2[i]=0;        }                // Length of the string        let n = s.length;        if (n == 1)            return true;                // traverse till the middle element        // is reached        for (let 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 (let i = 0; i < MAX_CHAR; i++)            if (count1[i] != count2[i])                return false;                return true;    }            // Driver program to test above function         // String to be checked    let  s = "abab";    if (checkCorrectOrNot(s))        document.write("Yes");    else        document.write("No");         //This code is contributed by avanitrachhadiya2155     </script>
Output : 
YES
Time Complexity : O(n), where n is the length of the string.
Auxiliary Space :  O(1)
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.
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++
Java
Python3
C#
PHP
Javascript
// 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 split// string or notbool checkCorrectOrNot(string s){    // Counter array initialized 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 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 functionint main(){    // String to be checked    string s = "abab";     if (checkCorrectOrNot(s))        cout << "Yes\n";    else        cout << "No\n";    return 0;}
// Java program to check if it two// half of string contain same Character// set or notpublic class GFG {     static final int MAX_CHAR = 26;          // function to check both halves    // for equality    static boolean checkCorrectOrNot(String s)    {        // Counter array initialized 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 program to check if it is# possible to split string or notMAX_CHAR = 26 # Function to check if we # can split string or notdef checkCorrectOrNot(s):         global MAX_CHAR         # Counter array initialized 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    # different, set flag to 1    for i in range(MAX_CHAR):                 if count[i] != 0:            return False     return True  # Driver Code # String to be checkeds = "abab" print("Yes" if checkCorrectOrNot(s) else "No")  # This code is contributed by Ansu Kumari.
// C# program to check if it two// half of string contain same Character// set or notusing System; public class GFG {     static int MAX_CHAR = 26;         // function to check both halves    // for equality    static bool checkCorrectOrNot(String s)    {                 // Counter array initialized 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 program to check if it is// possible to split string or not$MAX_CHAR = 26; // function to check if we// can split string or notfunction checkCorrectOrNot($s){    global $MAX_CHAR;         // Counter array initialized 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[$j] - 'a']--;    }     // Checking if values are    // different set flag to 1    for ($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?>
<script> // Javascript program to check if it two// half of string contain same Character// set or not     let MAX_CHAR = 26; // Function to check both halves// for equalityfunction checkCorrectOrNot(s){         // Counter array initialized with 0    let count = new Array(MAX_CHAR);    for(let i = 0; i < count.length; i++)    {        count[i] = 0;    }       // Length of the string    let n = s.length;    if (n == 1)        return true;       // Traverse till the middle element    // is reached    for(let 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(let i = 0; i < MAX_CHAR; i++)        if (count[i] != 0)            return false;       return true;} // Driver Codelet s = "abab"; if (checkCorrectOrNot(s))    document.write("Yes");else    document.write("No"); // This code is contributed by rag2127     </script>
Output: 
YES
 Time Complexity : O(n)
Auxiliary Space: O(1)This article is contributed by Sahil Rajput. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to review-team@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above. 
parashar
nitin mittal
ukasp
shubham_singh
avanitrachhadiya2155
rag2127
akshaysingh98088
adnanirshad158
shivamanandrj9
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