Find all the patterns of “1(0+)1” in a given string | SET 1(General Approach)

A string contains patterns of the form 1(0+)1 where (0+) represents any non-empty consecutive sequence of 0’s. Count all such patterns. The patterns are allowed to overlap.

Note : It contains digits and lowercase characters only. The string is not necessarily a binary. 100201 is not a valid pattern.
One approach to solve the problem is discussed here, other using Regular expressions is given in Set 2
Examples:

Input : 1101001
Output : 2

Input : 100001abc101
Output : 2

Let size of input string be n.
1. Iterate through index ‘0’ to ‘n-1’.
2. If we encounter a ‘1’, we iterate till the elements are ‘0’.
3. After the stream of zeros ends, we check whether we encounter a ‘1’ or not.
4. Keep on doing this till we reach the end of string.

Below is the implementation of the above method.

C++

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/* Code to count 1(0+)1 patterns in a string */
#include <bits/stdc++.h>
using namespace std;
  
/* Function to count patterns */
int patternCount(string str)
{
    /* Variable to store the last character*/
    char last = str[0];
  
    int i = 1, counter = 0;
    while (i < str.size())
    {
        /* We found 0 and last character was '1',
          state change*/
        if (str[i] == '0' && last == '1')
        {
            while (str[i] == '0')
                i++;
  
            /* After the stream of 0's, we got a '1',
               counter incremented*/
            if (str[i] == '1')
                counter++;
        }
  
        /* Last character stored */
        last = str[i];
        i++;
    }
  
    return counter;
}
  
/* Driver Code */
int main()
{
    string str = "1001ab010abc01001";
    cout << patternCount(str) << endl;
    return 0;
}

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Java














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// Java Code to count 1(0+)1  


// patterns in a string  


import java.io.*; 


  


class GFG  


{ 


    // Function to count patterns  


    static int patternCount(String str) 


    { 


        /* Variable to store the last character*/


        char last = str.charAt(0); 


      


        int i = 1, counter = 0; 


        while (i < str.length()) 


        { 


            /* We found 0 and last character was '1', 


            state change*/


            if (str.charAt(i) == '0' && last == '1') 


            { 


                while (str.charAt(i) == '0') 


                    i++; 


      


                // After the stream of 0's, we  


                // got a '1',counter incremented 


                if (str.charAt(i) == '1') 


                    counter++; 


            } 


      


            /* Last character stored */


            last = str.charAt(i); 


            i++; 


        } 


      


        return counter; 


    } 


      


    // Driver Code  


    public static void main (String[] args) 


    { 


        String str = "1001ab010abc01001"; 


        System.out.println(patternCount(str)); 


          


    } 


} 


  


// This code is contributed by vt_m. 



















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Python3














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# Python3 code to count 1(0+)1 patterns in a  


  


# Function to count patterns  


def patternCount(str): 


      


    # Variable to store the last character 


    last = str[0] 


  


    i = 1; counter = 0


    while (i < len(str)): 


          


        # We found 0 and last character was '1', 


        # state change 


        if (str[i] == '0' and last == '1'): 


            while (str[i] == '0'): 


                i += 1


                  


                # After the stream of 0's, we got a '1', 


                # counter incremented 


                if (str[i] == '1'):  


                    counter += 1


          


        # Last character stored  


        last = str[i] 


        i += 1


      


    return counter 


  


  


# Driver Code  


str = "1001ab010abc01001"


ans = patternCount(str) 


print (ans) 


      


# This code is contributed by saloni1297 



















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C#














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// C# Code to count 1(0 + )1  


// patterns in a string  


using System; 


  


class GFG  


{ 


      


    // Function to count patterns  


    static int patternCount(String str) 


    { 


        // Variable to store the  


        // last character 


        char last = str[0]; 


      


        int i = 1, counter = 0; 


        while (i < str.Length) 


        { 


            // We found 0 and last  


            // character was '1', 


            // state change 


            if (str[i] == '0' && last == '1') 


            { 


                while (str[i] == '0') 


                    i++; 


      


                // After the stream of 0's, we  


                // got a '1',counter incremented 


                if (str[i] == '1') 


                    counter++; 


            } 


      


            // Last character stored  


            last = str[i]; 


            i++; 


        } 


      


        return counter; 


    } 


      


    // Driver Code  


    public static void Main () 


    { 


        String str = "1001ab010abc01001"; 


        Console.Write(patternCount(str)); 


          


    } 


} 


  


// This code is contributed by nitin mittal 



















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PHP














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<?php 


// PHP Code to count 1(0+)1 patterns  


// in a string 


  


// Function to count patterns 


function patternCount($str) 


{ 


      


    // Variable to store the  


    // last character 


    $last = $str[0]; 


  


    $i = 1;  


    $counter = 0; 


    while ($i < strlen($str)) 


    { 


          


        // We found 0 and last character 


        // was '1', state change 


        if ($str[$i] == '0' && $last == '1') 


        { 


            while ($str[$i] == '0') 


                $i++; 


  


            // After the stream of 0's, 


            // we got a '1', counter  


            // incremented 


            if ($str[$i] == '1') 


                $counter++; 


        } 


  


        /* Last character stored */


        $last = $str[$i]; 


        $i++; 


    } 


  


    return $counter; 


} 


  


    // Driver Code 


    $str = "1001ab010abc01001"; 


    echo patternCount($str) ; 


  


// This code is contributed by nitin mittal 


?> 



















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Output :


2



This article is contributed by Rohit Thapliyal. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.


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