[LeetCode-Algorithms-89] "Gray Code" (2017.12.26-WEEK17)
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题目链接:Gray Code
- 题目描述:
The gray code is a binary numeral system where two successive values differ in only one bit.
Given a non-negative integer n representing the total number of bits in the code, print the sequence of gray code. A gray code sequence must begin with 0.
For example, given n = 2, return[0,1,3,2]
. Its gray code sequence is:
00 - 001 - 111 - 310 - 2
Note:
For a given n, a gray code sequence is not uniquely defined.For example, [0,2,3,1] is also a valid gray code sequence according to the above definition.
For now, the judge is able to judge based on one instance of gray code sequence. Sorry about that.
(1)思路:格雷码有一个小规律就是n位格雷码后分别再加0/1就有了n+1位格雷码。本来我想的是给后面加位数,但是发现实现起来不如直接往前加1方便。
举个例子,2位格雷码:
00011110
要变成3位格雷码,给最高位之前加1就好了,但是必须从后往前循环。
000001011010110111101100
(2)代码:
class Solution {public: vector<int> grayCode(int n) { vector<int> ans(1, 0); for(int i = 0; i < n; i++) { int size = ans.size(); while(size--) { int ans_temp = ans[size]; ans_temp += (1 << i); ans.push_back(ans_temp); } } return ans; }};
(3)提交结果:
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