66. Plus One

Source: Dev.to

Problem Description

You are given a large integer represented as an integer array digits, where each digits[i] is the iᵗʰ digit of the integer. The digits are ordered from most significant to least significant (left‑to‑right). The integer does not contain any leading zeros.

Task: Increment the integer by one and return the resulting array of digits.

Examples

Constraints

• 1 = 0; $i--) {

Solution (PHP)

<?php
function plusOne(array $digits): array {
    $carry = 1;
    for ($i = count($digits) - 1; $i >= 0; $i--) {
        $sum = $digits[$i] + $carry;
        $digits[$i] = $sum % 10;
        $carry = intdiv($sum, 10);
        if ($carry === 0) {
            break; // no further propagation needed
        }
    }
    if ($carry === 1) {
        array_unshift($digits, 1);
    }
    return $digits;
}

// Test cases
print_r(plusOne([1, 2, 3]));   // [1, 2, 4]
print_r(plusOne([4, 3, 2, 1])); // [4, 3, 2, 2]
print_r(plusOne([9]));          // [1, 0]
?>