19.2.23 [LeetCode 89] Gray Code
阿新 • • 發佈:2019-02-23
一個 位數 mil pla -- click seq NPU splay
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].
題意
怎麽說呢,很腦殘
就在這道題的世界觀裏,一個二進制數只有其中一個位跟另一個數不一樣,這兩個數就可以成為相鄰關系
給位數求順序集合
題解
那就遞歸一下,每次遞歸都把n-1的結果反著遍歷一遍,可以保證是相鄰關系
1 class Solution { 2 public: 3 vector<int> grayCode(int n) { 4 vector<intView Code>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 };
19.2.23 [LeetCode 89] Gray Code