【LeetCode】89. Gray Code [미완성 미완성]

2991 단어 LeetCode
제목:
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 = 2^n, which for n = 0 the size is 2^0 = 1.
             Therefore, for n = 0 the gray code sequence is [0].

 

n , ,

 

1 1, ....

, ( ),

, ...

 

:( , 1 )

class Solution {
public:
	vector grayCode(int n) {
		vector> number;
		for(int i = 0; i <= n; ++ i) {
			vector temp;
			number.push_back(temp);
		}
		
		int max_number = 1 << n;
		for(int i = 0; i < max_number; ++ i) {
			int count = count_number(i);
			number[count].push_back(i);
            // cout << i << "  " << count << endl;
		}
		// cout << endl;
        
		vector result;
		
		int index = 0, cnt = max_number;
		while (cnt) {
			while (index < n && number[index].size()) {
				// cout << index << cnt << endl;
				result.push_back(number[index][0]);
				number[index].erase(number[index].begin());
				++ index;
				--cnt;
				
			}
			index -= 2;
			while (index >= 0 && number[index].size()) {
				// cout << index << cnt << endl;
				result.push_back(number[index][0]);
				number[index].erase(number[index].begin());
				-- index;
				-- cnt;
			}
			index += 2;
		}
		
		return result;
	}
	
	int count_number(int i) {
		int result = 0;
		while (i) {
			if (i & 1) {
				++ result;
			}
			i >>= 1;
		}
		return result;
	}
};

 

class Solution {
public:
	vector grayCode(int n) {         
		vector result;
		result.push_back(0);
		for (int i = 0; i < n; ++i) {
			int size = result.size();
			while (size--) {
				int curNum = result[size];
				curNum += (1 << i);
				result.push_back(curNum);
			}
		}
		return result;
	}
};

 

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