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

Recommended: Please solve it on “PRACTICE ” first, before moving on to the solution.

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++

/* 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; 
} 

Java

// 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. 

Python3

# 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 

C#

// 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 

PHP

<?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 
?> 

Output :

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My Personal Notes

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

Recommended: Please solve it on “PRACTICE ” first, before moving on to the solution.

C++

Java

Python3

C#

PHP

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