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Count of substrings of a Binary string containing only 1s

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  • Difficulty Level : Medium
  • Last Updated : 30 Mar, 2022
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Given a binary string of length N, we need to find out how many substrings of this string contain only 1s.

Examples: 

Input: S = “0110111”
Output: 9
Explanation:
There are 9 substring with only 1’s characters. 
“1” comes 5 times. 
“11” comes 3 times. 
“111” comes 1 time.

Input: S = “000”
Output: 0

Approach: The idea is to traverse the binary string and count the consecutive ones in the string. Below is the illustration of the approach:

  • Traverse the given binary string from index 0 to length – 1
  • Count the number of consecutive “1” till index i.
  • For each new character str[i], there will be more substring with all character’s as “1”

Below is the implementation of the above approach:

C++




// C++ implementation to find
// count of substring containing
// only ones
 
#include <bits/stdc++.h>
using namespace std;
 
// Function to find the total number
// of substring having only ones
int countOfSubstringWithOnlyOnes(string s)
{
    int res = 0, count = 0;
    for (int i = 0; i < s.length(); i++) {
    count = s[i] == '1' ? count + 1 : 0;
    res = (res + count);
    }
    return res;
}
 
// Driver Code
int main()
{
    string s = "0110111";
    cout << countOfSubstringWithOnlyOnes(s)
        << endl;
    return 0;
}

Java




// Java implementation to find
// count of substring containing
// only ones
class GFG{
     
// Function to find the total number
// of substring having only ones
static int countOfSubstringWithOnlyOnes(String s)
{
    int res = 0, count = 0;
    for(int i = 0; i < s.length(); i++)
    {
        count = s.charAt(i) == '1' ? count + 1 : 0;
        res = (res + count);
    }
    return res;
}
 
// Driver code
public static void main(String[] args)
{
    String s = "0110111";
     
    System.out.println(countOfSubstringWithOnlyOnes(s));
}
}
 
// This code is contributed by dewantipandeydp

Python3




# Python3 implementation to find
# count of substring containing
# only ones
 
# Function to find the total number
# of substring having only ones
def countOfSubstringWithOnlyOnes(s):
 
    count = 0
    res = 0
     
    for i in range(0,len(s)):
        if s[i] == '1':
            count = count + 1
        else:
            count = 0;
             
        res = res + count
             
    return res
 
# Driver Code
s = "0110111"
print(countOfSubstringWithOnlyOnes(s))
 
# This code is contributed by jojo9911

C#




// C# implementation to find count
// of substring containing only ones
using System;
 
class GFG{
     
// Function to find the total number
// of substring having only ones
static int countOfSubstringWithOnlyOnes(string s)
{
    int res = 0, count = 0;
     
    for(int i = 0; i < s.Length; i++)
    {
        count = s[i] == '1' ? count + 1 : 0;
        res = (res + count);
    }
    return res;
}
 
// Driver code
public static void Main(string[] args)
{
    string s = "0110111";
     
    Console.Write(countOfSubstringWithOnlyOnes(s));
}
}
 
// This code is contributed by rutvik_56

Javascript




<script>
 
// Javascript implementation to find
// count of substring containing
// only ones
 
// Function to find the total number
// of substring having only ones
function countOfSubstringWithOnlyOnes(s)
{
    var res = 0, count = 0;
    for (var i = 0; i < s.length; i++) {
    count = s[i] == '1' ? count + 1 : 0;
    res = (res + count);
    }
    return res;
}
 
// Driver Code
var s = "0110111";
document.write( countOfSubstringWithOnlyOnes(s));
 
</script>

Output

9

Time Complexity: O(n), where n is the size of the given string
Auxiliary Space: O(1)


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