FrogImp.php

<?php

/*
A small frog wants to get to the other side of the road. The frog is currently located
at position X and wants to get to a position greater than or equal to Y.
The small frog always jumps a fixed distance, D.

Count the minimal number of jumps that the small frog must perform to reach its target.

Write a function:

    function solution($X, $Y, $D);

that, given three integers X, Y and D, returns the minimal number of jumps
from position X to a position equal to or greater than Y.

For example, given:

  X = 10
  Y = 85
  D = 30

the function should return 3, because the frog will be positioned as follows:

        after the first jump, at position 10 + 30 = 40
        after the second jump, at position 10 + 30 + 30 = 70
        after the third jump, at position 10 + 30 + 30 + 30 = 100

Assume that:
        X, Y and D are integers within the range [1..1,000,000,000];
        X ≤ Y.

Complexity:
        expected worst-case time complexity is O(1);
        expected worst-case space complexity is O(1).
*/

/**
 * FrogJmp task.
 *
 * CODILITY ANALYSIS: https://codility.com/demo/results/training56G4RN-ZUE/
 * LEVEL: EASY
 * Correctness: 100%
 * Performance: 100%
 * Task score:  100%
 *
 * @param int $X Frog current position X
 * @param int $Y Minimal ending position Y
 * @param int $D Frog jump fixed distance, D
 *
 * @return int Minimal number of jumps from position X to a position equal to or greater than Y
 */
function solution($X, $Y, $D)
{
    // Distance between end ($Y) and start ($X) position
    $distance = $Y - $X;
    // Number of jumps needed to reach or surpass end position
    $jumps = (int) ceil($distance / $D);

    return $jumps;
}