19.2.23 [LeetCode 89] Gray Code
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.
Example 1:
Input: 2
Output: [0,1,3,2]
Explanation:
00 - 0
01 - 1
11 - 3
10 - 2
For a given n, a gray code sequence may not be uniquely defined.
For example, [0,2,3,1] is also a valid gray code sequence.
00 - 0
10 - 2
11 - 3
01 - 1
Example 2:
Input: 0
Output: [0]
Explanation: We define the gray code sequence to begin with 0.
A gray code sequence of n has size = 2n, which for n = 0 the size is 20 = 1.
Therefore, for n = 0 the gray code sequence is [0].
题意
怎么说呢,很脑残
就在这道题的世界观里,一个二进制数只有其中一个位跟另一个数不一样,这两个数就可以成为相邻关系
给位数求顺序集合
题解
那就递归一下,每次递归都把n-1的结果反着遍历一遍,可以保证是相邻关系
1 class Solution { 2 public: 3 vector<int> grayCode(int n) { 4 vector<int>ans; 5 if (n == 0) { 6 ans.push_back(0); 7 return ans; 8 } 9 ans = grayCode(n - 1); 10 int m = ans.size(), pls = (1 << (n - 1)); 11 for (int i = m - 1; i >= 0; i--) 12 ans.push_back(pls + ans[i]); 13 return ans; 14 } 15 };
注定失败的战争,也要拼尽全力去打赢它;
就算输,也要输得足够漂亮。