Given two strings 
and 
. Find the longest common prefix between them after performing zero or more operations on string . In each operation, you can swap any two letters.
Examples:
Input : a = "here", b = "there" Output : 4 The 2nd string can be made "heret" by just swapping characters and thus the longest prefix is of length 4. Input : a = "you", b = "me" Output : 0
Given that we are only allowed to performs swaps in the string and the length of prefix should be maximized. So the idea is to traverse string and check if the frequency of current character in string is same or less of that in string . If yes then move forward in string an otherwise break and print the length of the part of string an up to which a character is matched in string .
Below is the implementation of the above approach:
C++
// C++ program to find the longest// common prefix between two strings // after performing swaps on the second string#include <bits/stdc++.h>using namespace std; void LengthLCP(string x, string y){ int fr[26]={0}; int a = x.length(); // length of x int b = y.length(); // length of y for (int i=0 ;i<b ; i++) { // creating frequency array of // characters of y fr[y[i] - 97] += 1; } // storing the length of // longest common prefix int c = 0; for (int i=0 ;i<a ; i++) { // checking if the frequency of the character at // position i in x in b is greater than zero or not // if zero we increase the prefix count by 1 if (fr[x[i] - 97] > 0){ c += 1; fr[x[i] - 97] -= 1; } else break; } cout<<(c)<<endl;}// Driver Codeint main(){string x="here", y = "there"; LengthLCP(x, y);return 0;}//contributed by Arnab Kundu |
Java
// Java program to find the longest// common prefix between two strings // after performing swaps on the second stringpublic class GFG { static void LengthLCP(String x, String y) { int fr[]=new int [26]; int a = x.length(); // length of x int b = y.length(); // length of y for (int i=0 ;i<b ; i++) { // creating frequency array of // characters of y fr[y.charAt(i) - 97] += 1; } // storing the length of // longest common prefix int c = 0; for (int i=0 ;i<a ; i++) { // checking if the frequency of the character at // position i in x in b is greater than zero or not // if zero we increase the prefix count by 1 if (fr[x.charAt(i) - 97] > 0){ c += 1; fr[x.charAt(i) - 97] -= 1; } else break; } System.out.println((c)) ; } public static void main(String args[]) { String x="here", y = "there"; LengthLCP(x, y); } // This code is contributed by ANKITRAI1} |
Python3
# Python program to find the longest# common prefix between two strings # after performing swaps on the second stringdef LengthLCP(x, y): fr = [0] * 26 a = len(x) # length of x b = len(y) # length of y for i in range(b): # creating frequency array of # characters of y fr[ord(y[i]) - 97] += 1 # storing the length of # longest common prefix c = 0 for i in range(a): # checking if the frequency of the character at # position i in x in b is greater than zero or not # if zero we increase the prefix count by 1 if (fr[ord(x[i]) - 97] > 0): c += 1 fr[ord(x[i]) - 97] -= 1 else: break print(c)# Driver Codex, y = "here", "there"LengthLCP(x, y) |
C#
// C# program to find the longest // common prefix between two strings // after performing swaps on the // second stringusing System;class GFG { static void LengthLCP(String x, String y) { int []fr = new int [26]; int a = x.Length; // length of x int b = y.Length; // length of y for (int i = 0 ; i < b; i++) { // creating frequency array // of characters of y fr[y[i] - 97] += 1; } // storing the length of // longest common prefix int c = 0; for (int i = 0 ; i < a; i++) { // checking if the frequency of // the character at position i // in x in b is greater than zero // or not if zero we increase the // prefix count by 1 if (fr[x[i] - 97] > 0) { c += 1; fr[x[i] - 97] -= 1; } else break; } Console.Write((c)) ; } // Driver Codepublic static void Main() { String x = "here", y = "there"; LengthLCP(x, y); } } // This code is contributed by 29AjayKumar |
PHP
<?php // PHP program to find the longest// common prefix between two strings // after performing swaps on the second stringfunction LengthLCP($x, $y){ $fr = array_fill(0,26,NULL); $a = strlen($x); // length of x $b = strlen($y); // length of y for ($i = 0 ;$i < $b ; $i++) { // creating frequency array of // characters of y $fr[ord($y[$i]) - 97] += 1; } // storing the length of // longest common prefix $c = 0; for ($i = 0 ;$i < $a ; $i++) { // checking if the frequency of the character at // position i in x in b is greater than zero or not // if zero we increase the prefix count by 1 if ($fr[ord($x[$i]) - 97] > 0) { $c += 1; $fr[ord($x[$i]) - 97] -= 1; } else break; } echo $c;}// Driver Code$x="here";$y = "there";LengthLCP($x, $y);return 0;// This code is contributed by ChitraNayal?> |
Javascript
<script>// JavaScript program to find the long// common prefix between two strings // after performing swaps on the second string function LengthLCP(x, y) { let fr = Array(26).fill(0); let a = x.length; // length of x let b = y.length; // length of y for (let i=0 ;i<b ; i++) { // creating frequency array of // characters of y fr[y[i].charCodeAt() - 97] += 1; } // storing the length of // longest common prefix let c = 0; for (let i=0 ;i<a ; i++) { // checking if the // frequency of the character at // position i in x in b is greater // than zero or not // if zero we increase the // prefix count by 1 if (fr[x[i].charCodeAt() - 97] > 0){ c += 1; fr[x[i].charCodeAt() - 97] -= 1; } else break; } document.write((c)) ; }// driver code let x="here", y = "there"; LengthLCP(x, y); </script> |
Output:
4
Time Complexity: O(length(x) + length(y))
Space Complexity: O(26)
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