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Minimum number of deletions to make a string palindrome in C++.
Problem statement
Given a string of size ‘n’. The task is to delete a minimum number of characters to make string palindrome.
If the given string is “abcda” then we can delete any 2 characters except first and last to make it a palindrome.
If we delete character ‘b’ and ‘c’ then “ada” string is a palindrome
If we delete character ‘c’ and ‘d’ then “aba” string is a palindrome
If we delete character ‘b’ and ‘d’ then “aca” string is a palindrome
Algorithm
1. Find longest palindromic subsequence of given string. Let’s call it as “lpsSize”. 2. Minimum characters to be deleted = (length of string – lpsSize) Code.
Example
#include <iostream>
#include <algorithm>
using namespace std;
int lps(string s, int i, int j){
if (i == j) {
return 1;
}
if (s[i] == s[j] && i + 1 == j) {
return 2;
}
if (s[i] == s[j]) {
return lps(s, i + 1, j - 1) + 2;
}
return max(lps(s, i, j - 1), lps(s, i + 1, j));
}
int minDeletion(string s){
int n = s.size();
int lpsSize = lps(s, 0, n);
return (n - lpsSize);
}
int main(){
cout << "Minimum characters to be deleted = " <<
minDeletion("abcda") << endl;
return 0;
}Output
When you compile and execute the above program. It generates the following output −
Minimum characters to be deleted = 2
Updated on: 31-Oct-2019
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