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leetcode--Gray Code

2024-07-07 08:52:00   224人阅读

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

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.

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public class Solution {
    /**We start from 00...0 and 000...1. Changing i-th bit for each for them is same as to
     * add pow(2, i) to them.    *
     * @param n  --Integer, the length of the binary string
     * @return List<Integer> --all possible
     * @author Averill Zheng
     * @version 2014-06-05
     * @since JDK 1.7
     */
    public List<Integer> grayCode(int n) {
        List<Integer> result = new ArrayList<Integer>();
        result.add(0);
        if(n > 0){
            result.add(1);
            int length = 2;
            for(int i = 1; i < n; ++i){
                for(int j = length - 1; j > -1; --j)
                    result.add(result.get(j) + (int)Math.pow(2, i));
                length *= 2;
            }
        }
        return result;
    }
}

　　


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