[LeetCode] Plus One 简要分析
2016-03-08 13:09
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前言
Plus one是一道数组相关的题,其实就是高精度加法。题目
https://leetcode.com/problems/plus-one/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.
分析
因为数组头存储的是最高位,而数组尾存储的是个位,按照“正常”的加法思路,咱们是得倒着加的。在这个过程中维护一个进位值即可,具体见代码。代码
class Solution { public: vector<int> plusOne(vector<int>& digits) { int carry = 1;//进位 for (auto it = digits.rbegin(); it != digits.rend(); it++) {//从数组尾倒着遍历到数组头 *it += carry; carry = *it/10; *it %= 10; } if (carry != 0) digits.insert(digits.begin(), 1);//此时还有进位,在数组头插入“1” return digits; } };
更简练的写法:
class Solution { public: vector<int> plusOne(vector<int> &digits) { bool carry = true; for(int i=digits.size()-1; i >= 0 && carry; i--) { carry = (++digits[i]%=10) == 0; } if(carry) { digits.insert(digits.begin(), 1); } return digits; } };
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