LeetCode-Solutions-in-Cpp17

Solutions to high-frequency interview questions of LeetCode in C++17, taking into account both efficiency and comprehensibility.

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• 对各种情况依次处理

class Solution {
 public:
  vector<int> plusOne(vector<int>& digits) {
    int n = digits.size() - 1;
    if (digits[n] != 9) {  // 末位不为 9，直接加 1 返回即可
      ++digits[n];
      return digits;
    }
    while (digits[n] == 9) {  // 末尾有多个 9，均改为 0
      digits[n] = 0;
      if (--n < 0) {  // 如果全是 9，首位改为 1，末位加一个 0
        digits[0] = 1;
        digits.emplace_back(0);
        return digits;
      }
    }
    ++digits[n];  // 多个 9 但不全是 9，最后一个 9 的下一位加 1
    return digits;
  }
};

• 或者直接视为一个数从低位到高位依次计算

class Solution {
 public:
  vector<int> plusOne(vector<int>& digits) {
    int carry = 1;
    for (auto it = digits.rbegin(); it != digits.rend(); ++it) {
      if (!carry) {
        break;
      }
      *it += carry;
      carry = *it / 10;
      *it %= 10;
    }
    if (carry) {
      digits.emplace(digits.begin(), carry);
    }
    return digits;
  }
};