Given a string of lowercase letters. Find minimum characters to be inserted in string so that it can become palindrome. We can change positions of characters in string.
Examples:
Input : geeksforgeeks Output : 2 geeksforgeeks can be changed as: geeksroforskeeg geeksorfroskeeg and many more Input : aabbc Output : 0 aabbc can be changed as: abcba bacab
A palindromic string can have one odd character only when length of string is odd otherwise all characters occur even number of times. So, we have to find characters which occur odd times in a string.
The idea is to count occurrence of each character in a string. As palindromic string can have one character which occur odd times so number of insertion will be one less then count of characters which occur odd times. And if string is already palindrome, we do not need to add any character so result will be 0.
C++
// CPP program to find minimum number // of insertions to make a string // palindrome #include <bits/stdc++.h> using namespace std; // Function will return number of // characters to be added int minInsertion(string str) { // To store string length int n = str.length(); // To store number of characters // occurring odd number of times int res = 0; // To store count of each // character int count[26] = { 0 }; // To store occurrence of each // character for (int i = 0; i < n; i++) count[str[i] - 'a']++; // To count characters with odd // occurrence for (int i = 0; i < 26; i++) if (count[i] % 2 == 1) res++; // As one character can be odd return // res - 1 but if string is already // palindrome return 0 return (res == 0) ? 0 : res - 1; } // Driver program int main() { string str = "geeksforgeeks"; cout << minInsertion(str); return 0; } |
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Java
// Java program to find minimum number // of insertions to make a string // palindrome public class Palindrome { // Function will return number of // characters to be added static int minInsertion(String str) { // To store string length int n = str.length(); // To store number of characters // occurring odd number of times int res = 0; // To store count of each // character int[] count = new int[26]; // To store occurrence of each // character for (int i = 0; i < n; i++) count[str.charAt(i) - 'a']++; // To count characters with odd // occurrence for (int i = 0; i < 26; i++) { if (count[i] % 2 == 1) res++; } // As one character can be odd return // res - 1 but if string is already // palindrome return 0 return (res == 0) ? 0 : res - 1; } // Driver program public static void main(String[] args) { String str = "geeksforgeeks"; System.out.println(minInsertion(str)); } } |
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Python3
# Python3 program to find minimum number # of insertions to make a string # palindrome import math as mt # Function will return number of # characters to be added def minInsertion(tr1): # To store str1ing length n = len(str1) # To store number of characters # occurring odd number of times res = 0 # To store count of each # character count = [0 for i in range(26)] # To store occurrence of each # character for i in range(n): count[ord(str1[i]) - ord('a')] += 1 # To count characters with odd # occurrence for i in range(26): if (count[i] % 2 == 1): res += 1 # As one character can be odd return # res - 1 but if str1ing is already # palindrome return 0 if (res == 0): return 0 else: return res - 1 # Driver Code str1 = "geeksforgeeks"print(minInsertion(str1)) # This code is contributed by # Mohit kumar 29 |
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C#
// C# program to find minimum number // of insertions to make a string // palindrome using System; public class GFG { // Function will return number of // characters to be added static int minInsertion(String str) { // To store string length int n = str.Length; // To store number of characters // occurring odd number of times int res = 0; // To store count of each // character int[] count = new int[26]; // To store occurrence of each // character for (int i = 0; i < n; i++) count[str[i] - 'a']++; // To count characters with odd // occurrence for (int i = 0; i < 26; i++) { if (count[i] % 2 == 1) res++; } // As one character can be odd // return res - 1 but if string // is already palindrome // return 0 return (res == 0) ? 0 : res - 1; } // Driver program public static void Main() { string str = "geeksforgeeks"; Console.WriteLine(minInsertion(str)); } } // This code is contributed by vt_m. |
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PHP
<?php // PHP program to find minimum number // of insertions to make a string // palindrome // Function will return number of // characters to be added function minInsertion($str) { // To store string length $n = strlen($str); // To store number of characters // occurring odd number of times $res = 0; // To store count of each // character $count = array(26); // To store occurrence of each // character for ($i = 0; $i < $n; $i++) $count[ord($str[$i]) - ord('a')]++; // To count characters with odd // occurrence for ($i = 0; $i < 26; $i++) { if ($count[$i] % 2 == 1) $res++; } // As one character can be odd return // res - 1 but if string is already // palindrome return 0 return ($res == 0) ? 0 : $res - 1; } // Driver program $str = "geeksforgeeks"; echo(minInsertion($str)); // This code is contributed // by Mukul Singh ?> |
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Output:
2
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