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:
- 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++
// 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 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 int main() { // String to be checked string s = "abab"; if (checkCorrectOrNot(s)) cout << "Yes\n"; else cout << "No\n"; return 0; } |
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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 |
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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 # 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. |
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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 |
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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[$j] - 'a']++; } // Checking if values are // different set flag to 1 for ($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 ?> |
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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 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 int main() { // String to be checked string s = "abab"; if (checkCorrectOrNot(s)) cout << "Yes\n"; else cout << "No\n"; return 0; } |
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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 |
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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 # 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. |
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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. |
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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[$j] - 'a']--; } // Checking if values are // different set flag to 1 for ($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 ?> |
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Output:
YES
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