Minimum steps to remove substring 010 from a binary string

Given a binary string, the task is to count the minimum steps to remove substring “010” from this binary string.

Examples:

Input: binary_string = “0101010” 
Output: 2 
Switching 0 to 1 at index 2 and index 4 will remove the substring 010. 
Hence the number of steps needed is 2. 

Input: binary_string = “010” 
Output: 1 
Switching any one 0 to 1 or 1 to 0 will remove the substring 010. 
Hence the number of steps needed is 1.

Approach: 

1. Iterate the string from beginning to end-2 of the binary string.
2. If in binary string continuously three characters are ‘0’, ‘1’, ‘0’ then any one character can be change so that one step will be count.
3. Increase the loop counter by 2.

Below is the implementation of the above approach: 

C++

// CPP program to calculate steps
// to remove substring 010
// from a binary string

#include <bits/stdc++.h>
using namespace std;

// Function to find the minimum steps
int minSteps(string str)
{

    int count = 0;

    for (int i = 0; i < str.length() - 2; i++) {

        if (str[i] == '0') {
            if (str[i + 1] == '1') {
                if (str[i + 2] == '0') {

                    // substring "010" found
                    count++;
                    i += 2;
                }
            }
        }
    }

    return count;
}

// Driver code
int main()
{

    // Get the binary string
    string str = "0101010";

    // Find the minimum steps
    cout << minSteps(str);

    return 0;
}

Java

// Java program to calculate steps
// to remove substring 010
// from a binary string
import java.util.*;

class GFG{

// Function to find the minimum steps
static int minSteps(String str)
{

    int count = 0;

    for (int i = 0; i < str.length() - 2; i++) {

        if (((int)str.charAt(i)) == '0') {
            if (str.charAt(i + 1) == '1') {
                if (str.charAt(i + 2) == '0') {

                    // substring "010" found
                    count++;
                    i += 2;
                }
            }
        }
    }

    return count;
}

// Driver code
public static void main(String args[])
{

    // Get the binary string
    String str = "0101010";

    // Find the minimum steps
    System.out.println(minSteps(str));
}
}

Python3

# Python3 program to calculate steps
# to remove substring 010
# from a binary string

# Function to find the minimum steps
def minSteps(str):

    count = 0
    i = 0
    while i < len(str) - 2:
        if str[i] == '0':
            if(str[i + 1] == '1'):
                if(str[i + 2] == '0'):

                    # substring "010" found
                    count = count + 1
                    i = i + 2
        i = i + 1

    return count

# Driver code

# Get the binary string
str = "0101010"

# Find the minimum steps
print(minSteps(str))

# This code is contributed
# by Shashank_Sharma

C#

// C# program to calculate steps
// to remove substring 010
// from a binary string
using System;

class GFG
{

// Function to find the minimum steps
static int minSteps(string str)
{
    int count = 0;

    for (int i = 0; i < str.Length - 2; i++)
    {

        if (((int)str[i]) == '0')
        {
            if (str[i + 1] == '1')
            {
                if (str[i + 2] == '0')
                {

                    // substring "010" found
                    count++;
                    i += 2;
                }
            }
        }
    }

    return count;
}

// Driver code
public static void Main()
{

    // Get the binary string
    string str = "0101010";

    // Find the minimum steps
    Console.Write(minSteps(str));
}
}

// This code is contributed by ChitraNayal

PHP

<?php
// PHP program to calculate steps to remove
// substring 010 from a binary string

// Function to find the minimum steps
function minSteps($str)
{
    $count = 0;

    for ($i = 0; $i < strlen($str) - 2; $i++)
    {

        if ($str[$i] == '0')
        {
            if ($str[$i + 1] == '1')
            {
                if ($str[$i + 2] == '0')
                {

                    // substring "010" found
                    $count++;
                    $i += 2;
                }
            }
        }
    }

    return $count;
}

// Driver code

// Get the binary string
$str = "0101010";

// Find the minimum steps
echo(minSteps($str));

// This code is contributed
// by Shivi_Aggarwal
?>

Javascript

<script>

// js program to calculate steps
// to remove substring 010
// from a binary string

// Function to find the minimum steps
function minSteps(str)
{
    let count = 0;

    for (let i = 0; i < str.length - 2; i++)
    {

        if ((str[i]) == '0')
        {
            if (str[i + 1] == '1')
            {
                if (str[i + 2] == '0')
                {

                    // substring "010" found
                    count++;
                    i += 2;
                }
            }
        }
    }

    return count;
}

// Driver code

// Get the binary string
let str = "0101010";

// Find the minimum steps
document.write(minSteps(str));

// This code is contributed by mohit kumar 29.

</script>

Output

2

Time complexity: O(n) where n is the length of binary string

Auxiliary Space: O(1)