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Minimum removal of consecutive similar characters required to empty a Binary String
  • Last Updated : 21 May, 2021

Given a binary string S of length N, the task is to find the minimum number of removal of adjacent similar characters required to empty the given binary string.

Examples:

Input: S = “1100011“
Output: 2
Explanation:
Operation 1: Removal of all 0s modifies S to “1111“.
Operation 2: Removal of all remaining 1s makes S empty.
Therefore, the minimum number of operations required is 2.

Input: S = “0010100“
Output: 3
Explanation:
Operation 1: Removal of all 1s modifies S to “000100“.
Operation 2: Removal of all 1s modifies S = “00000“.
Operation 3: Removal of all remaining 0s makes S empty.
Therefore, the minimum number of operations required is 3.

Approach: The given problem can be solved using Greedy Approach. The idea is to delete the consecutive occurrences of the character with a higher frequency. Follow the steps below to solve the problem:



  • Traverse the given string S and generate a new string, say newString, by removing consecutive occurrences of the character with higher frequency.
  • Finally, print (sizeof(newString) + 1)/2 as the required answer

Below is the implementation of the above approach:

C++




// C++ program for the above approach
 
#include <bits/stdc++.h>
using namespace std;
 
// Function to find minimum steps
// to make the string empty
int minSteps(string S)
{
    // Stores the modified string
    string new_str;
 
    // Size of string
    int N = S.length();
 
    int i = 0;
 
    while (i < N) {
 
        new_str += S[i];
 
        // Removing substring of same
        // character from modified string
        int j = i;
        while (i < N && S[i] == S[j])
            ++i;
    }
 
    // Print the minimum steps required
    cout << ceil((new_str.size() + 1) / 2.0);
}
 
// Driver Code
int main()
{
    // Given string S
    string S = "0010100";
 
    // Function Call
    minSteps(S);
 
    return 0;
}

Java




// Java program for the above approach
import java.util.*;
 
class GFG{
 
// Function to find minimum steps
// to make the String empty
static void minSteps(String S)
{
     
    // Stores the modified String
    String new_str = "";
 
    // Size of String
    int N = S.length();
 
    int i = 0;
 
    while (i < N)
    {
        new_str += S.charAt(i);
         
        // Removing subString of same
        // character from modified String
        int j = i;
        while (i < N && S.charAt(i) == S.charAt(j))
            ++i;
    }
 
    // Print the minimum steps required
    System.out.print((int)Math.ceil(
        (new_str.length() + 1) / 2.0));
}
 
// Driver Code
public static void main(String[] args)
{
     
    // Given String S
    String S = "0010100";
 
    // Function Call
    minSteps(S);
}
}
 
// This code is contributed by Princi Singh

Python3




# Python3 program for the above approach
from math import ceil
 
# Function to find minimum steps
# to make the empty
def minSteps(S):
     
    # Stores the modified string
    new_str = ""
 
    # Size of string
    N = len(S)
 
    i = 0
 
    while (i < N):
        new_str += S[i]
 
        # Removing substring of same character
        # from modified string
        j = i
        while (i < N and S[i] == S[j]):
            i += 1
 
    # Print the minimum steps required
    print(ceil((len(new_str) + 1) / 2))
 
# Driver Code
if __name__ == '__main__':
     
    # Given S
    S = "0010100"
 
    # Function Call
    minSteps(S)
 
# This code is contributed by mohit kumar 29

C#




// C# program for the above approach
using System;
 
class GFG{
 
// Function to find minimum steps
// to make the string empty
static void minSteps(string S)
{
     
    // Stores the modified string
    string new_str = "";
     
    // Size of string
    int N = S.Length;
 
    int i = 0;
 
    while (i < N)
    {
        new_str += S[i];
         
        // Removing substring of same
        // character from modified string
        int j = i;
         
        while (i < N && S[i] == S[j])
            ++i;
    }
 
    // Print the minimum steps required
    Console.Write((int)Math.Ceiling(
        (new_str.Length + 1) / 2.0));
}
 
// Driver Code
public static void Main()
{
     
    // Given string S
    string S = "0010100";
 
    // Function Call
    minSteps(S);
}
}
 
// This code is contributed by SURENDRA_GANGWAR

Javascript




<script>
// Javascript program to implement
// the above approach
 
// Function to find minimum steps
// to make the string empty
function minSteps(S)
{
      
    // Stores the modified string
    let new_str = "";
      
    // Size of string
    let N = S.length;
  
    let i = 0;
  
    while (i < N)
    {
        new_str += S[i];
          
        // Removing substring of same
        // character from modified string
        let j = i;
          
        while (i < N && S[i] == S[j])
            ++i;
    }
  
    // Prlet the minimum steps required
    document.write(Math.ceil(
        (new_str.length + 1) / 2.0));
}
 
    // Driver Code
     
    // Given string S
    let S = "0010100";
  
    // Function Call
    minSteps(S)
      
</script>
Output: 
3

 

Time Complexity: O(N)
Auxiliary Space: O(1)

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