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Check if a string can become empty by recursively deleting a given sub-string

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  • Difficulty Level : Easy
  • Last Updated : 19 Jun, 2022

Given a string “str” and another string “sub_str”. We are allowed to delete “sub_str” from “str” any number of times. It is also given that the “sub_str” appears only once at a time. The task is to find if “str” can become empty by removing “sub_str” again and again.
Examples: 
 

Input  : str = "GEEGEEKSKS", sub_str = "GEEKS"
Output : Yes
Explanation : In the string GEEGEEKSKS, we can first 
              delete the substring GEEKS from position 4.
              The new string now becomes GEEKS. We can 
              again delete sub-string GEEKS from position 1. 
              Now the string becomes empty.


Input  : str = "GEEGEEKSSGEK", sub_str = "GEEKS"
Output : No
Explanation : In the string it is not possible to make the
              string empty in any possible manner.

 

Method#1: A simple solution to solve this problem is by using inbuilt string functions find() and erase(). First input the sub-string substr for searching purpose in the original string str, then iterate the original string to find the index of sub-string using find() which return starting index of the sub-string in the original string else -1 if not found and erase that sub-string using erase() until length of original string is greater than 0.
The above simple solutions works because the given substring appears only once at a time. 
 

C++




// C++ Program to check if a string can be
// converted to an empty string by deleting
// given sub-string from any position, any
// number of times.
#include<bits/stdc++.h>
using namespace std;
 
// Returns true if str can be made empty by
// recursively removing sub_str.
bool canBecomeEmpty(string str, string sub_str)
{
    while (str.size() > 0)
    {
        // idx: to store starting index of sub-
        //      string found in the original string
        int idx = str.find(sub_str);
        if (idx == -1)
            break;
 
        // Erasing the found sub-string from
        // the original string
        str.erase(idx, sub_str.size());
    }
 
    return (str.size() == 0);
}
 
// Driver code
int main()
{
    string str = "GEEGEEKSKS", sub_str = "GEEKS";
    if (canBecomeEmpty(str, sub_str))
        cout<<"\nYes";
    else
        cout<<"\nNo";
    return 0;
}

Java




//Java program to check if a string can be
// converted to an empty string by deleting
// given sub-string from any position, any
// number of times.
 
class GFG {
 
// Returns true if str can be made empty by
// recursively removing sub_str.
    static boolean canBecomeEmpty(String str, String sub_str) {
        while (str.length() > 0) {
            // idx: to store starting index of sub-
            //      string found in the original string
            int idx = str.indexOf(sub_str);
            if (idx == -1) {
                break;
            }
 
            // Erasing the found sub-string from
            // the original string
            str = str.replaceFirst(sub_str,"");
        }
 
        return (str.length() == 0);
    }
 
// Driver code
    public static void main(String[] args) {
        String str = "GEEGEEKSKS", sub_str = "GEEKS";
        if (canBecomeEmpty(str, sub_str)) {
            System.out.print("\nYes");
        } else {
            System.out.print("\nNo");
        }
    }
}
// This code is contributed by 29AjayKumar

Python3




# Python3 program to check if a string can be
# converted to an empty string by deleting
# given sub-string from any position, any
# number of times.
 
# Returns true if str can be made empty by
# recursively removing sub_str.
def canBecomeEmpty(string, sub_str):
    while len(string) > 0:
 
        # idx: to store starting index of sub-
        #     string found in the original string
        idx = string.find(sub_str)
 
        if idx == -1:
            break
 
        # Erasing the found sub-string from
        # the original string
        string = string.replace(sub_str, "", 1)
 
    return (len(string) == 0)
 
# Driver code
if __name__ == "__main__":
    string = "GEEGEEKSKS"
    sub_str = "GEEKS"
    if canBecomeEmpty(string, sub_str):
        print("Yes")
    else:
        print("No")
 
# This code is contributed by
# sanjeev2552

C#




// C# program to check if a string can be
// converted to an empty string by deleting
// given sub-string from any position, any
// number of times.
using System;
     
class GFG
{
 
    // Returns true if str can be made empty by
    // recursively removing sub_str.
    static Boolean canBecomeEmpty(String str, String sub_str)
    {
        while (str.Length > 0)
        {
            // idx: to store starting index of sub-
            //     string found in the original string
            int idx = str.IndexOf(sub_str);
            if (idx == -1)
            {
                break;
            }
 
            // Erasing the found sub-string from
            // the original string
            str = str.Replace(sub_str,"");
        }
 
        return (str.Length == 0);
    }
 
    // Driver code
    public static void Main(String[] args)
    {
        String str = "GEEGEEKSKS", sub_str = "GEEKS";
        if (canBecomeEmpty(str, sub_str))
        {
            Console.Write("\nYes");
        }
        else
        {
            Console.Write("\nNo");
        }
    }
}
 
// This code is contributed by 29AjayKumar

Javascript




<script>
// Javascript program to check if a string can be
// converted to an empty string by deleting
// given sub-string from any position, any
// number of times.
 
// Returns true if str can be made empty by
// recursively removing sub_str
function canBecomeEmpty(str,sub_str)
{
    while (str.length > 0)
    {
     
            // idx: to store starting index of sub-
            //      string found in the original string
            let idx = str.indexOf(sub_str);
            if (idx == -1) {
                break;
            }
   
            // Erasing the found sub-string from
            // the original string
            str = str.replace(sub_str,"");
        }
   
        return (str.length == 0);
}
 
// Driver code
let str = "GEEGEEKSKS", sub_str = "GEEKS";
if (canBecomeEmpty(str, sub_str)) {
    document.write("<br>Yes");
} else {
    document.write("<br>No");
}
 
 
// This code is contributed by rag2127
</script>

Output

Yes

Method#2: One possible solution would be to use the regular expression. Regular expressions module are very helpful with string. Regular expression module has search function which is used to find the patterns in string. And replace function is used for replacing the characters of string. Follow are steps for our approach:

  • Use the re.search function on string to find the pattern in string. 
  • Use the re.replace function to replace the sub-string from string. 
  • Repeat step one and two until there is sub-string in string after replacing it. 
  • At last if string is empty after all replacing then it can become empty else it cannot become empty.

C++




// C++ Program to check if a string can be
// converted to an empty string by deleting
// given sub-string from any position, any
// number of times.
#include<bits/stdc++.h>
using namespace std;
 
 
// Returns true if str can be made empty by
// recursively removing sub_str.
bool canBecomeEmpty(string str1 , string sub_str){
     
    regex r(sub_str);
    smatch m ;
    // matches words beginning by "Geek"
     
    while(regex_search(str1, m, r)){
//     regex_replace() for replacing the match with 'geek'
    
    str1 = regex_replace(str1, r, "");
    }
 
// Returing result
    return true ? str1=="" : false ;
     
}
 
// Driver code
int main()
{
    string s = "GeeksForGeeGeeksks";
    string k = "Geeks";
    if (canBecomeEmpty(s, k)){
        cout << "\nYes" ;
    }
    else {
        cout << "\nNo";
        }
         
    return 0;
}

Python3




# Python3 program to check if a string can be
# converted to an empty string by deleting
# given sub-string from any position, any
# number of times.
  
# Returns true if str can be made empty by
# recursively removing sub_str.
import re
 
 
def canBecomeEmpty(string, sub_str):
    # finding sub-string in string
    while sub_str in string :
        # Replacing sub-string from string
        string = re.sub(sub_str, "", string)
    # Returning result
    return True if string == "" else False
     
     
# Driver code
if __name__ == "__main__":
    string = "GeeksforGeeGeeksks"
    sub_str = "Geeks"
    if canBecomeEmpty(string, sub_str):
        print("Yes")
    else:
        print("No")
         
  
# This code is contributed by
# sanjeev2552

Javascript




// Javascript program to check if a string can be
// converted to an empty string by deleting
// given sub-string from any position, any
// number of times.
 
// Returns true if str can be made empty by
// recursively removing sub_str
function canBecomeEmpty(str,sub_str)
{  
    // Regular expression for sub_string
    const regex = new RegExp(sub_str);
    // Iterating over string untill it matches sub_string
    while(regex.test(str)){
        // Replacing sub-string from string
    str = str.replace(regex, '')
         
    }
    // Returning result
        return false ? str : true ;
}
 
// Driver code
let str = "GeeksForGeeGeeksks", sub_str = "Geeks";
if (canBecomeEmpty(str, sub_str)) {
    console.log("Yes");
} else {
    console.log("No");
}
 
 
// This code is contributed by sam snehil

Output

No

This article is contributed by Himanshu Gupta. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to review-team@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.
 


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