Count of non-overlapping sub-strings “101” and “010” in the given binary string

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Given binary string str, the task is to find the count of non-overlapping sub-strings of either the form “010” or “101”.

Examples:

Input: str = “10101010101”
Output: 3
str[0..2] = “101”
str[3..5] = “010”
str[6..8] = “101”
Input: str = “111111111111110”
Output: 0

Approach: Initialize count = 0 and for every index i in the given string check whether the sub-string of size 3 starting at the current index i matches either with “010” or “101”. If it’s a match then update count = count + 1 and i = i + 3 (to avoid overlapping of sub-strings) else increment i by 1.
Below is the implementation of the above approach:

C++

// C++ implementation of the approach
#include <iostream>
using namespace std;
 
// Function to return the count of
// required non-overlapping sub-strings
int countSubStr(string &s, int n)
{
 
    // To store the required count
    int count = 0;
    for (int i = 0; i < n - 2;) {
 
        // If "010" matches the sub-string
        // starting at current index i
        if (s[i] == '0' && s[i + 1] == '1'
            && s[i + 2] == '0') {
            count++;
            i += 3;
        }
 
        // If "101" matches the sub-string
        // starting at current index i
        else if (s[i] == '1' && s[i + 1] == '0'
                 && s[i + 2] == '1') {
            count++;
            i += 3;
        }
        else {
            i++;
        }
    }
 
    return count;
}
 
// Driver code
int main()
{
    string s = "10101010101";
    int n = s.length();
 
    cout << countSubStr(s, n);
 
    return 0;
}

Java

// Java implementation of the approach
class GFG 
{
    // Function to return the count of
    // required non-overlapping sub-strings
    static int countSubStr(char[] s, int n)
    {
 
        // To store the required count
        int count = 0;
        for (int i = 0; i < n - 2😉 
        {
 
            // If "010" matches the sub-string
            // starting at current index i
            if (s[i] == '0' && s[i + 1] == '1'
                    && s[i + 2] == '0')
            {
                count++;
                i += 3;
            } 
            // If "101" matches the sub-string
            // starting at current index i
            else if (s[i] == '1' && s[i + 1] == '0'
                    && s[i + 2] == '1') 
            {
                count++;
                i += 3;
            }
            else
             
            {
                i++;
            }
        }
 
        return count;
    }
 
    // Driver code
    public static void main(String[] args)
    {
        char[] s = "10101010101".toCharArray();
        int n = s.length;
 
        System.out.println(countSubStr(s, n));
    }
}
 
// This code is contributed by 29AjayKumar

Python3

# Python3 implementation of the approach 
 
# Function to return the count of 
# required non-overlapping sub-strings 
def countSubStr(s, n) :
 
    # To store the required count 
    count = 0; 
    i = 0
     
    while i < (n-2) : 
 
        # If "010" matches the sub-string 
        # starting at current index i 
        if (s[i] == '0' and s[i + 1] == '1'and s[i + 2] == '0') : 
            count += 1; 
            i += 3; 
 
        # If "101" matches the sub-string 
        # starting at current index i 
        elif (s[i] == '1' and s[i + 1] == '0'and s[i + 2] == '1') :
            count += 1; 
            i += 3; 
         
        else :
            i += 1; 
 
    return count; 
 
 
# Driver code 
if __name__ == "__main__" : 
 
    s = "10101010101"; 
    n = len(s); 
 
    print(countSubStr(s, n)); 
 
# This code is contributed by AnkitRai01

C#

// C# implementation of the approach
using System;
     
class GFG 
{
    // Function to return the count of
    // required non-overlapping sub-strings
    static int countSubStr(char[] s, int n)
    {
 
        // To store the required count
        int count = 0;
        for (int i = 0; i < n - 2;) 
        {
 
            // If "010" matches the sub-string
            // starting at current index i
            if (s[i] == '0' && 
                s[i + 1] == '1' && 
                s[i + 2] == '0')
            {
                count++;
                i += 3;
            } 
             
            // If "101" matches the sub-string
            // starting at current index i
            else if (s[i] == '1' && 
                     s[i + 1] == '0' && 
                     s[i + 2] == '1') 
            {
                count++;
                i += 3;
            }
            else
            {
                i++;
            }
        }
 
        return count;
    }
 
    // Driver code
    public static void Main(String[] args)
    {
        char[] s = "10101010101".ToCharArray();
        int n = s.Length;
 
        Console.WriteLine(countSubStr(s, n));
    }
}
 
// This code is contributed by Rajput-Ji

Javascript

<script>
// javascript implementation of the approach
 
    // Function to return the count of
    // required non-overlapping sub-strings
    function countSubStr( s , n) {
 
        // To store the required count
        var count = 0;
        for (i = 0; i < n - 2;) {
 
            // If "010" matches the sub-string
            // starting at current index i
            if (s[i] == '0' && s[i + 1] == '1' && s[i + 2] == '0') {
                count++;
                i += 3;
            }
            // If "101" matches the sub-string
            // starting at current index i
            else if (s[i] == '1' && s[i + 1] == '0' && s[i + 2] == '1') {
                count++;
                i += 3;
            } else
 
            {
                i++;
            }
        }
 
        return count;
    }
 
    // Driver code
     
        var s = "10101010101";
        var n = s.length;
 
        document.write(countSubStr(s, n));
 
// This code contributed by Rajput-Ji
</script>

Output:

Time Complexity: O(n), where n is the length of the string.
Auxiliary Space: O(1) as constant extra space is used

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