Author: Mrinal

Problem:
You are given an array of integers. On each move you are allowed to increase exactly one of its element by one. Find the minimal number of moves required to obtain a strictly increasing sequence from the input.

Solution:

function arrayChange($inputArray) {
    $count = 0;
        
    foreach ( $inputArray as $key => $value ) {
        $is_less = isset( $key ) && isset( $inputArray[ $key-1 ] ) && $value <= $inputArray[ $key-1 ];
        if ( $is_less ) {        
            $inputArray[ $key ] = ( $inputArray[ $key - 1 ] ) + 1;
            $count += $inputArray[ $key-1 ]- $value + 1;
        }
    }
  
    return $count;
}

To develop a simple calculator class in the context of PHP is more fun with __call() magic method.

class Calculator {
    public function __call($method, $args) {
        if (isset($this->$method)) {
            $func = $this->$method;
            return call_user_func_array($func, $args);
        }
    }
}

$calculator = new Calculator();
$calculator->add = function ( $a1, $a2 ) { echo $a1 + $a2; };
$calculator->subs = function( $a1, $a2 ) { echo $a1 - $a2; };
$calculator->multi = function( $a1, $a2 ) { echo $a1 * $a2; };
$calculator->div = function( $a1, $a2 ) { echo $a1 / $a2; };

Problem:

Two arrays are called similar if one can be obtained from another by swapping at most one pair of elements in one of the arrays.

Given two arrays a and b, check whether they are similar.

Example

• For a = [1, 2, 3] and b = [1, 2, 3], the output should be
  areSimilar(a, b) = true.The arrays are equal, no need to swap any elements.
• For a = [1, 2, 3] and b = [2, 1, 3], the output should be
  areSimilar(a, b) = true.We can obtain b from a by swapping 2 and 1 in b.
• For a = [1, 2, 2] and b = [2, 1, 1], the output should be
  areSimilar(a, b) = false.Any swap of any two elements either in a or in b won’t make a and b equal.

Solution:

function areSimilar($a, $b) {
    $array_difference = array_diff_assoc($a, $b);
    if( empty( $array_difference )) return true;
    if( count($array_difference) === 2) {
        $b_a_array_difference = array_diff_assoc($b, $a);
        $is_equal = array_diff($array_difference, $b_a_array_difference);
        if(!empty($is_equal)) {
            return false;
        }
        return true;
    }
    return false;
}

Problem: How to add numbers between 1 to 100?

This obey arithmetic sequence. Mathematical formula wise this is 100*(1+100)/2=1050. Here is details.

Let see how to implement this in PHP.

function sum( $n, $a1, $a2 ) {
    return $n * ( $a1 + $a2 ) / 2;
}
echo 'Total=' . sum( 100, 1, 100 );