66. Plus One

1. 问题描述

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

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

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Tags: Array Math
Similar Problems: (M) Multiply Strings (E) Add Binary

2. 解答思路

3. 代码

#include <vector>
using namespace std;
class Solution {
public:
    vector<int> plusOne_method_1(vector<int>& digits) {
        if (digits.empty())
        {
            digits.push_back(1);
            return digits;
        }
        return puls(digits, digits.size()-1, 1);
    }
    vector<int> plusOne_method_2(vector<int>& digits) {
        if (digits.empty())
        {
            digits.push_back(1);
            return digits;
        }
        int nTakeOver = 1;
        int i;
        for (i=digits.size()-1; i>=0; i--)
        {
            int sum = digits[i] + nTakeOver;
            digits[i] = sum%10;
            nTakeOver = sum/10;
            if (0 == nTakeOver)
            {
                return digits;
            }
        }
        if (1 == nTakeOver)
        {
            digits.insert(digits.begin(), 1);
        }
        return digits;
    }
private:
    vector<int> puls(vector<int>& digits, int idx, int nTakeOver = 0)
    {
        int sum = digits[idx] + nTakeOver;
        digits[idx] = sum%10;
        nTakeOver = sum/10;
        if (0 == nTakeOver)
        {
            return digits;
        }
        if (0 == idx)
        {
            digits.insert(digits.begin(), 1);
            return digits;
        }
        return puls(digits, idx-1, 1);
    }
};

4. 反思

方法1. 递归实现

方法2. 循环实现