Check whether second string can be formed from characters of first string

Last Updated : 29 Sep, 2022

Given two strings str1 and str2, check if str2 can be formed from str1

Example :

Input : str1 = geekforgeeks, str2 = geeks
Output : Yes
Here, string2 can be formed from string1.

Input : str1 = geekforgeeks, str2 = and
Output : No
Here string2 cannot be formed from string1.

Input : str1 = geekforgeeks, str2 = geeeek
Output : Yes
Here string2 can be formed from string1
as string1 contains 'e' comes 4 times in
string2 which is present in string1.

The idea is to count frequencies of characters of str1 in a count array. Then traverse str2 and decrease frequency of characters of str2 in the count array. If frequency of a characters becomes negative at any point, return false.

Below is the implementation of above approach :

C++

// CPP program to check whether second string // can be formed from first string #include <bits/stdc++.h> using namespace std; const int MAX = 256;  bool canMakeStr2(string str1, string str2) {     // Create a count array and count frequencies     // characters in str1.     int count[MAX] = {0};     for (int i = 0; i < str1.length(); i++)         count[str1[i]]++;              // Now traverse through str2 to check     // if every character has enough counts     for (int i = 0; i < str2.length(); i++)     {         if (count[str2[i]] == 0)            return false;         count[str2[i]]--;     }     return true; }  // Driver Code int main() {     string str1 = "geekforgeeks";     string str2 = "for";     if (canMakeStr2(str1, str2))        cout << "Yes";     else        cout << "No";     return 0; }

Java

// Java program to check whether second string // can be formed from first string   class GFG {       static int MAX = 256;       static boolean canMakeStr2(String str1, String str2)     {         // Create a count array and count frequencies         // characters in str1.         int[] count = new int[MAX];         char []str3 = str1.toCharArray();         for (int i = 0; i < str3.length; i++)             count[str3[i]]++;           // Now traverse through str2 to check         // if every character has enough counts                  char []str4 = str2.toCharArray();         for (int i = 0; i < str4.length; i++) {             if (count[str4[i]] == 0)                 return false;             count[str4[i]]--;         }         return true;     }       // Driver Code     static public void main(String []args)     {         String str1 = "geekforgeeks";         String str2 = "for";         if (canMakeStr2(str1, str2))             System.out.println("Yes");         else             System.out.println("No");     } }

Python3

# Python program to check whether second string # can be formed from first string def canMakeStr2(s1, s2):      # Create a count array and count      # frequencies characters in s1     count = {s1[i] : 0 for i in range(len(s1))}          for i in range(len(s1)):         count[s1[i]] += 1          # Now traverse through str2 to check      # if every character has enough counts     for i in range(len(s2)):         if (count.get(s2[i]) == None or count[s2[i]] == 0):             return False         count[s2[i]] -= 1     return True  # Driver Code s1 = "geekforgeeks" s2 = "for"  if canMakeStr2(s1, s2):     print("Yes") else:     print("No")

// C# program to check whether second string // can be formed from first string using System;  class GFG {      static int MAX = 256;      static bool canMakeStr2(string str1, string str2)     {         // Create a count array and count frequencies         // characters in str1.         int[] count = new int[MAX];         for (int i = 0; i < str1.Length; i++)             count[str1[i]]++;          // Now traverse through str2 to check         // if every character has enough counts         for (int i = 0; i < str2.Length; i++) {             if (count[str2[i]] == 0)                 return false;             count[str2[i]]--;         }         return true;     }      // Driver Code     static public void Main()     {         string str1 = "geekforgeeks";         string str2 = "for";         if (canMakeStr2(str1, str2))             Console.WriteLine("Yes");         else             Console.WriteLine("No");     } }   // This code is contributed by vt_m.

PHP

<?php // PHP program to check whether  // second string can be formed  // from first string $MAX = 256;  function canMakeStr2($str1, $str2) {     // Create a count array and      // count frequencies characters      // in str1.     $count = (0);     for ($i = 0; $i < strlen($str1); $i++)          // Now traverse through str2      // to check if every character     // has enough counts     for ($i = 0; $i < strlen($str2); $i++)     {         if ($count[$str2[$i]] == 0)         return -1;     }     return true; }  // Driver Code $str1 = "geekforgeeks"; $str2 = "for"; if (canMakeStr2($str1, $str2)) echo "Yes"; else echo "No";  // This code is contributed by ajit ?>

JavaScript

<script>   // Javascript program to check whether second string   // can be formed from first string    function canMakeStr2(str1, str2)   {       // Create a count array and count frequencies       // characters in str1.       let count = {};       //         count.fill(0);       for (let i = 0; i < str1.length; i++) {           if (str1[i] in count)               count[str1[i]]++;           else               count[str1[i]] = 1       }        // Now traverse through str2 to check       // if every character has enough counts       for (let i = 0; i < str2.length; i++) {           if (count[str2[i]] == 0 || !(str2[i] in count))               return false;           count[str2[i]]--;       }       return true;   }    let str1 = "geekforgeeks";   let str2 = "gggeek";   if (canMakeStr2(str1, str2))       document.write("Yes");   else       document.write("No"); </script>

Output

Yes

Time Complexity: O(n+m), where n and m are the length of the given strings.
Auxiliary Space: O(256), which is constant.

Remove characters from the first string which are present in the second string

anuragrawat1

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Check whether second string can be formed from characters of first string

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