Count number of 0’s with given conditions

Given a binary string (containing 1’s and 0’s), write a program to count the number of 0’s in a given string such that the following conditions hold:

• 1’s and 0’s are in any order in a string
• Use of conditional statements like if, if..else, and switch are not allowed
• Use of  addition/subtraction is not allowed

Examples:

Input : S = “101101”
Output : 2

Input : S = “00101111000”
Output : 6

Approach: The above problem can be solved with the below idea:

If counter and conditional statements are not allowed. We are having option of Error handling.

Steps involved in the implementation of the approach:

• Take a string and a static variable counter which maintain the count of zero.
• Traverse through each character and convert it into an integer.
• Take this number and use it as a denominator of the number “0”.
• Use the exception handling method try..catch in a loop such that whenever we got the Arithmetic exception, the counter will increment.
• Print the counter value as a result.

Below is the implementation of the above approach:

C++

#include <iostream>
#include <string>

using namespace std;

// Counter for count the zero's
int cnt = 0;

// Function to calculate the number
// of 0's
void countZero(string s)
{
    for (int i = 0; i < s.length(); i++) {

        int div = s[i] - '0';
        // If we do 0/0 it gives
        // exception where we cnt
        // the number of 0's
        // and other are 1's

        if (div == 0)

            cnt++;
    }

    // Return the count of 0's
    cout << cnt << endl;
}

int main()
{
    string s = "101101";

    // Function call
    countZero(s);
}

Java

// Java implementation of the code
import java.io.*;

class GFG {

    // Counter for count the zero's
    public static int cnt = 0;

    public static void main(String[] args)
    {

        String s = "101101";

        // Function call
        countZero(s);
    }

    // Function to calculate the number
    // of 0's
    static void countZero(String s)
    {

        for (int i = 0; i < s.length(); i++) {
            try {
                int div = Character.getNumericValue(
                    s.charAt(i));
                // If we do 0/0 it gives
                // exception where we cnt
                // the number of 0's
                // and other are 1's
                int val = 0 / div;
            }

            // O is found
            catch (Exception exception) {
                cnt++;
            }
        }

        // Return the count of 0's
        System.out.println(cnt);
    }
}

Python3

cnt = 0


def count_zero(s: str):
    global cnt
    for i in range(len(s)):
        div = int(s[i])
        if div == 0:
            cnt += 1
    print(cnt)


s = "101101"
count_zero(s)

C#

using System;

class Program
{
    // Counter for count the zero's
    static int cnt = 0;

    // Function to calculate the number
    // of 0's
    static void CountZero(string s)
    {
        for (int i = 0; i < s.Length; i++)
        {
            int div = s[i] - '0';
            // If we do 0/0 it gives
            // exception where we cnt
            // the number of 0's
            // and other are 1's

            if (div == 0)
                cnt++;
        }

        // Return the count of 0's
        Console.WriteLine(cnt);
    }

    static void Main(string[] args)
    {
        string s = "101101";

        // Function call
        CountZero(s);
    }
}

Javascript

// Counter for count the zero's
let cnt = 0;

// Function to calculate the number
// of 0's
function countZero(s) {
    for (let i = 0; i < s.length; i++) {
        if (s[i] === '0') {
            cnt++;
        }
    }
    // Return the count of 0's
    console.log(cnt);
}

let s = "101101";

// Function call
countZero(s);

Output

2

Time Complexity: O(N)
Auxiliary Space: O(1)

An approach using XOR operation:

Follow the steps below to implement: 

• Iterate over the string.
  • The character 0 is represented as 48 in ASCII, so we can use XOR operation with 48 to check if the current character is 0.
  • If the character is 0, then XOR with 48 will result in 0, which will be added to the count variable.
  • If the character is 1, then XOR with 48 will result in 1, which will not affect the count variable.
• Finally, the number of zeros in the binary string is n – count, which is printed as the output.

C++

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

// Function to calculate the number
// of 0's
void countZero(string binary_string)
{
    int n = binary_string.length();
    int count = 0;
    for (int i = 0; i < n; i++) {
        count += binary_string[i] ^ 48;
    }
    cout << n - count << endl;
}

int main()
{
    string s = "101101";

    // Function call
    countZero(s);
}

Java

import java.util.*;

public class CountZero {
  public static void countZero(String binaryString) {
    int n = binaryString.length();
    int count = 0;
    for (int i = 0; i < n; i++) {
      count += binaryString.charAt(i) ^ 48;
    }
    System.out.println(n - count);
  }

  public static void main(String[] args) {
    String s = "101101";
    countZero(s);
  }
}

C#

using System;

public class Program
{
    static void countZero(string binaryString)
    {
        int n = binaryString.Length;
        int count = 0;
        for (int i = 0; i < n; i++)
        {
            count += binaryString[i] ^ 48;
        }
        Console.WriteLine(n - count);
    }

    static void Main(string[] args)
    {
        string s = "101101";
        countZero(s);
    }
}

Python3

def countZero(binary_string):
    n = len(binary_string)
    count = 0
    for i in range(n):
        count += ord(binary_string[i]) ^ 48
    print(n - count)

s = "101101"
countZero(s)

Javascript

function countZero(binaryString) {
    const n = binaryString.length;
    let count = 0;
    for (let i = 0; i < n; i++) {
        count += binaryString.charCodeAt(i) ^ 48;
    }
    console.log(n - count);
}

const s = "101101";
countZero(s);

Output

2

Time Complexity: O(N)
Auxiliary Space: O(1)