[LeetCode]66. Plus One 解题报告(C++)

[LeetCode]66. Plus One 解题报告(C++)

题目描述

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

The digits are stored such that the most significant digit is at the head of the list, and each element in the array contain a single digit.

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

Example 1:

Input: [1,2,3]
Output: [1,2,4]
Explanation: The array represents the integer 123.

Example 2:

Input: [4,3,2,1]
Output: [4,3,2,2]
Explanation: The array represents the integer 4321.

题目大意

• 给定一个数组.表示的是一个整数.
• 对最后一个数字加1.
• 求结果.

解题思路

方法1:

• 注意进位即可.

代码实现:

class Solution {
public:
    vector<int> plusOne(vector<int>& digits) {
        vector<int> res;
        int carry = 0;
        int n = digits.size();
        int num = 0;
        for (int i = n - 1; i >= 0; i--) {
            if (i == n - 1) {
                num = carry + digits[i] + 1;
            }
            else
            {
                num = carry + digits[i];
            }
            carry = num / 10;
            res.push_back(num % 10);
        }
        if (carry) {
            res.insert(res.begin(),1);
        }
        return res;

    }
};

方法2:

• 不开辟空间.直接在原来的数据上操作
• 注意9的情况.

代码实现

class Solution {
public:
    vector<int> plusOne(vector<int> &digits) {
        int n = digits.size();
        for (int i = n - 1; i >= 0; --i) {
            if (digits[i] == 9) digits[i] = 0;
            else {
                digits[i] += 1;
                return digits;
            }
        }
        if (digits.front() == 0) digits.insert(digits.begin(), 1);
        return digits;
    }
};

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小结

-