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 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:

1. Declare two counter arrays for keeping count of characters in two half of the string, each of size 26.
2. Now run a loop and take two variables i and j, where i starts from 0 and j starts from (length of string – 1).
3. 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.
4. 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.
5. If all counts matched, return true.

Below is the implementation of above idea:

C++

 `// C++ program to check if it is``// possible to split string or not``#include ``using` `namespace` `std;``const` `int` `MAX_CHAR = 26;` `// function to check if we can split``// string or not``bool` `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

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 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

 `# Python3 program to check if it is``# possible to split string or not``MAX_CHAR ``=` `26` `# Function to check if we ``# can split string or not``def` `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 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 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

 ``

Javascript

 ``

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.

1. We can solve this problem by using only 1 counter array.
2. Take a string and increment counts for first half and then decrement counts for second half.
3. 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 ``using` `namespace` `std;``const` `int` `MAX_CHAR = 26;` `// function to check if we can split``// string or not``bool` `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

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 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

 `# Python3 program to check if it is``# possible to split string or not``MAX_CHAR ``=` `26` `# Function to check if we  ``# can split string or not``def` `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 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 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

 ``

Javascript

 ``

Output
`Yes`

Time Complexity : O(n)
Auxiliary Space: O(1)

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