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Removing elements between the two zeros
  • Difficulty Level : Hard
  • Last Updated : 16 Jun, 2020

Given an integer N which shows the size of the string and in the next line given a string which contains a string of character with only zero and one. The task is to remove a single character each time that comes in between the two zero characters.

During each turn, only one character from the string will be removed that satisfies the following condition :

  • It must be surrounded by zeroes on both sides.

Examples:

Input  : str = "1001
Output : str = "1001"

Input  : str = "10101
Output : str = "1001"

Use a loop from 1 to N – 1 and check if any element lies between two zeros such that s[i – 1] = ‘0’ and s[i + 1] = ‘0’. If the condition is satisfied then, delete the character at that position, ad start searching for patterns again.

C++




// C++ program to delete elements between zeros
#include <bits/stdc++.h>
using namespace std;
  
// Function to find the string 
// after operation
string findstring(string s)
{
    int n = s.length();
          
    // Travesing through string 
    for (int i = 1; i < n - 1; i++)
    {
        // Checking for character 
        // Between two zeros
        if ((s.at(i - 1) == '0' && 
            s.at(i + 1) == '0'))
        {
  
            // deleting the character 
            // At specific position
            s.erase(i, 1);
              
            i--;
            if (i > 0 && s.at(i - 1) == '0')
                 i--;
                          
            // updating the length 
            // of the string
            n = s.length();
        }
    }
              
    return s;
}
      
// Drivers code
int main() {
      
    cout << findstring("100100");
    return 0;
}


Java




// Java program to delete elements between zeros
import java.util.*;
  
public class GFG 
{
    // Function to find the string 
    // after operation
    static String findstring(String s)
    {
        int n = s.length();
              
        // use for loop to remove the
        // character between two zeros
        for (int i = 1; i < n - 1; i++)
        
            // Checking for character 
            // Between two zeros
            if ((s.charAt(i - 1) == '0' && 
                 s.charAt(i + 1) == '0'))
            {
                      
                // deleting the character 
                // At specific position
                s = s.substring(0, i) + s.substring(i + 1);
                  
                i--;
                if (i > 0 && s.charAt(i - 1) == '0')
                    i--;
                          
                // updating the length 
                // of the string
                n = s.length();
            }
        }
              
        return s;
    }
      
    // Driver code
    public static void main(String[] args)
    {
       String s="100100";
       System.out.println(findstring(s));
    }
}


Python3




# Python3 program to delete elements
# between zeros
  
# Function to find the string
# after operation
def findstring(s):
      
    n = len(s)
    s = list(s)
    i = 1
  
    # Travesing through string
    while i < n - 1:
  
        # Checking for character
        # Between two zeros
        if (s[i - 1] == '0' and 
            s[i + 1] == '0'):
  
            # Deleting the character
            # At specific position
            s.pop(i)
  
            i -= 1
            if i > 0 and s[i - 1] == '0':
                i -= 1
  
            # Updating the length
            # of the string
            n = len(s)
        i += 1
  
    return ''.join(s)
  
# Driver code
if __name__ == '__main__':
  
    print (findstring('100100'))
  
# This code is contributed by rutvik_56


C#




// C# program to delete 
// elements between zeros
using System;
  
class GFG
{
    // Function to find the 
    // string after operation
    static string findstring(string s)
    {
        int n = s.Length;
        string st = "";
          
        // Travesing through string 
        for (int i = 1; i < n - 1; i++)
        {
            // Checking for character 
            // Between two zeros
            if ((s[i - 1] == '0' && 
                 s[i + 1] == '0'))
            {
      
                // deleting the character 
                // At specific position
                st = s.Remove(i, 1);
                s = st;
                  
                i--;
                if (i > 0 && 
                    s[i - 1] == '0')
                    i--;
                              
                // updating the length 
                // of the string
                n = s.Length;
            }
        }                 
        return s;
    }
      
    // Driver code
    static void Main()
    {
        Console.Write(findstring("100100"));
    }
}
  
// This code is contributed by 
// Manish Shaw(manishshaw1)


Output:

100

Time Complexity : O(N), where N is the size of input string.

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