Gray Code
[leetcode]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. For example, given n = 2, return [0,1,3,2]. Its gray code sequence is:
00 - 0 01 - 1 11 - 3 10 - 2
Gray Code, 每次看每次都不记得。写下来让自己好温习。
Gray Code 0 = 0, 下一项是toggle最右边的bit(LSB), 再下一项是toggle最右边值为 “1” bit的左边一个bit。然后重复
如: 3bit
Gray Code: 000, 001, 011, 010, 110, 111, 101, 100, 最右边值为 “1” 的bit在最左边了,结束。
Binary : 000, 001, 010, 011, 100, 101, 110, 111
再者就是Binary Code 转换为Gray Code了。
如:
Binary Code :1011 要转换成Gray Code
1011 = 1(照写第一位), 1(第一位与第二位异或 1^0 = 1), 1(第二位异或第三位, 0^1=1), 0 (1^1 =0) = 1110
其实就等于 (1011 >> 1) ^ 1011 = 1110
有了上面的等式写code就简单了
1 public ArrayList<Integer> grayCode(int n) { 2 int size=1<<n; 3 ArrayList<Integer> result=new ArrayList<>(size); 4 for(int i=0;i<size;i++) 5 { 6 result.add(i^(i>>1)); 7 } 8 return result; 9 }
http://www.cnblogs.com/lihaozy/archive/2012/12/31/2840437.html