PHP Program to Count Zeros and Ones in Binary Representation of a Number

Counting the number of zeros and ones in the binary representation of a number is a common task in computer science and programming. In this article, we will explore how to achieve this in PHP using different approaches.

Count Zeros and Ones in Binary Representation of a Number using Built-in Functions

This PHP program uses built-in functions to efficiently count the number of zeros and ones in the binary representation of a given number. It first converts the number to binary using decbin( ), then uses substr_count( ) to count the occurrences of “0” and “1” in the binary string. The counts are returned as an associative array.

Example: Implementation to count zeros and ones in binary representation of a number.

PHP

<?php

function countZeros_Ones($number) {
    $binary = decbin($number);
    $zeros = substr_count($binary, "0");
    $ones = substr_count($binary, "1");

    return ["zeros" => $zeros, "ones" => $ones];
}

// Driver code
$number = 10;
$result = countZeros_Ones($number);

echo "Binary representation of $number: " . decbin($number) . "\n";
echo "Number of zeros: " . $result["zeros"] . "\n";
echo "Number of ones: " . $result["ones"] . "\n";

?>

Output

Binary representation of 10: 1010
Number of zeros: 2
Number of ones: 2

Explanation:

• The decbin function converts the decimal number to its binary representation.
• The substr_count( ) function counts the number of occurrences of ‘0’ and ‘1’ in the binary string.
• The function returns an associative array containing the count of zeros and ones.

Count Zeros and Ones in Binary Representation of a Number using Bitwise Operations

This PHP program uses bitwise operations to count the number of zeros and ones in the binary representation of a given number. It iterates through each bit of the number, checking if it’s a zero or a one using the bitwise AND operator (‘&’). If it’s a one, it increments the $ones counter; otherwise, it increments the $zeros counter. The program then shifts the number one bit to the right (`$number >> 1`) to move to the next bit. This process continues until the number becomes zero. The counts are returned as an associative array.

Example: Implementation to count zeros and ones in binary representation of a number.

PHP

<?php

function countZeros_Ones($number) {
    $zeros = 0;
    $ones = 0;

    while ($number > 0) {
        if ($number & 1) {
            $ones++;
        } else {
            $zeros++;
        }
        $number = $number >> 1;
    }

    return ["zeros" => $zeros, "ones" => $ones];
}

// Driver code
$number = 99;
$result = countZeros_Ones($number);

echo "Binary representation of $number: " . decbin($number) . "\n";
echo "Number of zeros: " . $result["zeros"] . "\n";
echo "Number of ones: " . $result["ones"] . "\n";

?>

Output

Binary representation of 99: 1100011
Number of zeros: 3
Number of ones: 4

Explanation:

• The function uses a while loop to iterate through each bit of the number.
• The & operator is used to check if the least significant bit is 1 or 0.
• The >> operator is used to right shift the number by one bit in each iteration.
• The function keeps a count of zeros and ones and returns them in an associative array.

Count Zeros and Ones in Binary Representation of a Number using Recursive Approach

This PHP program counts the number of zeros and ones in the binary representation of a given number using a recursive approach. It recursively divides the number by 2, counting the remainder as either a zero or a one, until the number becomes zero. The counts are returned as an associative array.

Example: Implementation to count zeros and ones in binary representation of a number.

PHP

<?php

function countSetBits($n) {
    // Base case: if n is 0, return 0
    if ($n == 0)
        return 0;
    else
        // If the last bit is set, add 1; otherwise, add 0
        return ($n & 1) +
                countSetBits($n >> 1);
}

function countUnsetBits($n) {
    // Base case: if n is 0, return 0
    if ($n == 0)
        return 0;
    else
        // If the last bit is set, add 0; otherwise, add 1
        return !($n & 1) +
                countUnsetBits($n >> 1);
}

// Get value from user
$n = 99;

// Function calling
echo "Number of Ones in $n are: ".countSetBits($n)."\n";
echo "Number of Zeroes in $n are: ".countUnsetBits($n)."\n";
?>

Output

Number of Ones in 99 are: 4
Number of Zeroes in 99 are: 3

Explanation

• The code uses a recursive approach to count the number of ones and zeroes in the binary representation of a given number $n.
• Both functions countSetBits and countUnsetBits return zero when $n is zero, as there are no bits to count.
• The code uses bitwise AND (`&`) and right shift (`>>`) operations to check the last bit of `$n`. If the last bit is set (i.e., it’s a one), the function increments the count of ones. If the last bit is not set (i.e., it’s a zero), the function increments the count of zeroes.
• The code demonstrates the usage of the two functions by calling them with a sample value of `$n` (99 in this case). It then prints the count of ones and zeroes in the binary representation of `$n`.