leetcode - 66.Plus One

最新推荐文章于 2020-11-28 22:12:38 发布

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本文介绍了解决数组加一问题的两种不同算法方法。第一种方法采用递归方式，从数组末尾开始逐位相加并进位；第二种方法则通过遍历数组逆序检查每一位是否达到最大值9，若未达到则直接加一返回结果，否则将该位置为0并继续检查前一位。

Plus One

Given a non-negative integer represented as a non-empty array of digits, plus one to the integer.

You may assume the integer do not contain any leading zero, except the number 0 itself.

The digits are stored such that the most significant digit is at the head of the list.

Solution1:

  public int[] plusOne(int[] digits) {
    return plus(digits, digits.length - 1, 1);
  }

  private int[] plus(int[] digits, int end, int i) {
    if (i == 0) {
      return digits;
    }
    if (end == -1) {
      int[] _digits = new int[digits.length + 1];
      System.arraycopy(digits, 0, _digits, 1, digits.length);
      _digits[0] = i;
      return _digits;
    }

    int num = digits[end] + i;
    digits[end] = num % 10;
    return plus(digits, --end, num / 10);
  }

Solution2:

  public int[] plusOne(int[] digits) {
    int n = digits.length;
    for (int i = n - 1; i >= 0; i--) {
      if (digits[i] < 9) {
        digits[i]++;
        return digits;
      }

      digits[i] = 0;
    }

    int[] newNumber = new int[n + 1];
    newNumber[0] = 1;

    return newNumber;
  }