Write an efficient C function that takes two strings as arguments and removes the characters from first string which are present in second string (mask string).
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Algorithm: Let first input string be”test string” and the string which has characters to be removed from first string be “mask”
- Initialize:
res_ind = 0 /* index to keep track of processing of each character in i/p string */
ip_ind = 0 /* index to keep track of processing of each character in the resultant string */ - Construct count array from mask_str. Count array would be:
(We can use Boolean array here instead of int count array because we don’t need count, we need to know only if character is present in mask string)
count[‘a’] = 1
count[‘k’] = 1
count[‘m’] = 1
count[‘s’] = 1 - Process each character of the input string and if count of that character is 0 then only add the character to the resultant string.
str = “tet tringng” // ’s’ has been removed because ’s’ was present in mask_str but we we have got two extra characters “ng”
ip_ind = 11
res_ind = 9
Put a ‘\0′ at the end of the string?
Implementations:
C
#include <stdio.h> #include <stdlib.h> #define NO_OF_CHARS 256 /* Returns an array of size 256 containg count of characters in the passed char array */ int * getCharCountArray( char * str) { int * count = ( int *) calloc ( sizeof ( int ), NO_OF_CHARS); int i; for (i = 0; *(str + i); i++) count[*(str + i)]++; return count; } /* removeDirtyChars takes two string as arguments: First string (str) is the one from where function removes dirty characters. Second string is the string which contain all dirty characters which need to be removed from first string */ char * removeDirtyChars( char * str, char * mask_str) { int * count = getCharCountArray(mask_str); int ip_ind = 0, res_ind = 0; while (*(str + ip_ind)) { char temp = *(str + ip_ind); if (count[temp] == 0) { *(str + res_ind) = *(str + ip_ind); res_ind++; } ip_ind++; } /* After above step string is ngring. Removing extra "iittg" after string*/ *(str + res_ind) = '\0' ; return str; } /* Driver code*/ int main() { char str[] = "geeksforgeeks" ; char mask_str[] = "mask" ; printf ( "%s" , removeDirtyChars(str, mask_str)); return 0; } |
C++
// C++ program to remove duplicates, the order of // characters is not maintained in this progress #include <bits/stdc++.h> #define NO_OF_CHAR 256 using namespace std; int * getcountarray(string str2) { int * count = ( int *) calloc ( sizeof ( int ), NO_OF_CHAR); for ( int i = 0; i < str2.size(); i++) { count[str2[i]]++; } return count; } /* removeDirtyChars takes two string as arguments: First string (str1) is the one from where function removes dirty characters. Second string(str2) is the string which contain all dirty characters which need to be removed from first string */ string removeDirtyChars(string str1, string str2) { // str2 is the string // which is to be removed int * count = getcountarray(str2); string res; // ip_idx helps to keep // track of the first string int ip_idx = 0; while (ip_idx < str1.size()) { char temp = str1[ip_idx]; if (count[temp] == 0) { res.push_back(temp); } ip_idx++; } return res; } // Driver Code int main() { string str1 = "geeksforgeeks" ; string str2 = "mask" ; // Function call cout << removeDirtyChars(str1, str2) << endl; } |
Java
// Java program to remove duplicates, the order of // characters is not maintained in this program public class GFG { static final int NO_OF_CHARS = 256 ; /* Returns an array of size 256 containg count of characters in the passed char array */ static int [] getCharCountArray(String str) { int count[] = new int [NO_OF_CHARS]; for ( int i = 0 ; i < str.length(); i++) count[str.charAt(i)]++; return count; } /* removeDirtyChars takes two string as arguments: First string (str) is the one from where function removes dirty characters. Second string is the string which contain all dirty characters which need to be removed from first string */ static String removeDirtyChars(String str, String mask_str) { int count[] = getCharCountArray(mask_str); int ip_ind = 0 , res_ind = 0 ; char arr[] = str.toCharArray(); while (ip_ind != arr.length) { char temp = arr[ip_ind]; if (count[temp] == 0 ) { arr[res_ind] = arr[ip_ind]; res_ind++; } ip_ind++; } str = new String(arr); /* After above step string is ngring. Removing extra "iittg" after string*/ return str.substring( 0 , res_ind); } // Driver Code public static void main(String[] args) { String str = "geeksforgeeks" ; String mask_str = "mask" ; System.out.println(removeDirtyChars(str, mask_str)); } } |
Python
# Python program to remove characters # from first string which # are present in the second string NO_OF_CHARS = 256 # Utility function to convert # from string to list def toList(string): temp = [] for x in string: temp.append(x) return temp # Utility function to # convert from list to string def toString( List ): return ''.join( List ) # Returns an array of size # 256 containing count of characters # in the passed char array def getCharCountArray(string): count = [ 0 ] * NO_OF_CHARS for i in string: count[ ord (i)] + = 1 return count # removeDirtyChars takes two # string as arguments: First # string (str) is the one # from where function removes dirty # characters. Second string # is the string which contain all # dirty characters which need # to be removed from first string def removeDirtyChars(string, mask_string): count = getCharCountArray(mask_string) ip_ind = 0 res_ind = 0 temp = '' str_list = toList(string) while ip_ind ! = len (str_list): temp = str_list[ip_ind] if count[ ord (temp)] = = 0 : str_list[res_ind] = str_list[ip_ind] res_ind + = 1 ip_ind + = 1 # After above step string is ngring. # Removing extra "iittg" after string return toString(str_list[ 0 :res_ind]) # Driver code mask_string = "mask" string = "geeksforgeeks" print removeDirtyChars(string, mask_string) # This code is contributed by Bhavya Jain |
C#
// C# program to remove // duplicates, the order // of characters is not // maintained in this program using System; class GFG { static int NO_OF_CHARS = 256; /* Returns an array of size 256 containg count of characters in the passed char array */ static int [] getCharCountArray(String str) { int [] count = new int [NO_OF_CHARS]; for ( int i = 0; i < str.Length; i++) count[str[i]]++; return count; } /* removeDirtyChars takes two string as arguments: First string (str) is the one from where function removes dirty characters. Second string is the string which contain all dirty characters which need to be removed from first string */ static String removeDirtyChars(String str, String mask_str) { int [] count = getCharCountArray(mask_str); int ip_ind = 0, res_ind = 0; char [] arr = str.ToCharArray(); while (ip_ind != arr.Length) { char temp = arr[ip_ind]; if (count[temp] == 0) { arr[res_ind] = arr[ip_ind]; res_ind++; } ip_ind++; } str = new String(arr); /* After above step string is ngring. Removing extra "iittg" after string*/ return str.Substring(0, res_ind); } // Driver Code public static void Main() { String str = "geeksforgeeks" ; String mask_str = "mask" ; Console.WriteLine(removeDirtyChars(str, mask_str)); } } // This code is contributed by mits |
geeforgee
Time Complexity: O(m+n) Where m is the length of mask string and n is the length of the input string.
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