Viiisit [LeetCode] - 66. Plus One

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Problem - Plus One

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 in left-to-right order. The large integer does not contain any leading 0’s.

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

翻譯蒟蒻

給定一個整數陣列，其中每個元素表示整數的一位數字，並對最後一位數字加一，回傳新的陣列。

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要考慮到進位的可能性。

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• Example 1:

  Input: digits = [1,2,3]
  Output: [1,2,4]
  Explanation: The array represents the integer 123.
  Incrementing by one gives 123 + 1 = 124.
  Thus, the result should be [1,2,4].

• Example 2:

  Input: digits = [4,3,2,1]
  Output: [4,3,2,2]
  Explanation: The array represents the integer 4321.
  Incrementing by one gives 4321 + 1 = 4322.
  Thus, the result should be [4,3,2,2].

• Example 3:

  Input: digits = [9]
  Output: [1,0]
  Explanation: The array represents the integer 9.
  Incrementing by one gives 9 + 1 = 10.
  Thus, the result should be [1,0].

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Solution - JavaScript

/**
 * @param {number[]} digits
 * @return {number[]}
 */
var plusOne = function(digits) {
    let carry = 1;
    for (let i = digits.length - 1; i >= 0; i--) {
        let sum = digits[i] + carry;
        if (sum > 9) {
            digits[i] = sum % 10;
            carry = 1;
        } else {
            digits[i] = sum;
            carry = 0;
        }
    }
    if (carry === 1) {
        digits.unshift(1);
    }
    return digits;
};

Solution - Ruby

def plus_one(digits)
  carry = 1
  (digits.length - 1).downto(0) do |i|
    sum = digits[i] + carry
    digits[i] = sum % 10
    carry = sum / 10
  end
  digits.unshift(1) if carry == 1
  digits
end

Solution - PHP

function plusOne($digits) {
  $carry = 1;
  for ($i = count($digits) - 1; $i >= 0; $i--) {
    $sum = $digits[$i] + $carry;
    $digits[$i] = $sum % 10;
    $carry = (int)($sum / 10);
  }
  if ($carry) {
    array_unshift($digits, $carry);
  }
  return $digits;
}

PHP 方法筆記

• array_unshift 用於將一個或多個元素插入到陣列的開始處。

  函數的基本語法如下：

  array_unshift(array &$array, mixed $value1 [, mixed $value2 [, mixed $...]]): int
  
  // 這會修改傳入的陣列 $array，並將指定的值插入到陣列的開始處。然後，回傳新陣列的元素數量，也就是插入後陣列的長度。

  $fruits = array("banana", "apple", "orange");
  array_unshift($fruits, "grape", "cherry");
  print_r($fruits);
  
  // Array
  // (
  //  [0] => grape
  //  [1] => cherry
  //  [2] => banana
  //  [3] => apple
  //  [4] => orange
  // )

LeetCode 傳送門 - Plus One