leetcode url

Solutions

Brute Force

int numOfBits(int n) {
	int counts = 0;
	while (n != 0) {
		n = n & (n - 1);
		counts += 1;
	}
	return counts;
}

vector<int> countBits(int n) {
	vector<int> arr;
	for (int i = 0; i <= n; ++i) {
		arr.push_back(numOfBits(i));
	}
	return ret;
}

Analysis

Optimal Method

Use dynamic programming approach.

vector<int> coountBits(int n) {
	vector<int> ret;
	ret.push_back(0);
	for (int i = 1; i <= n; ++i) {
		ret.push_back(ret[i >> 2] + (i & 1));
	}
	return ret;
}

Analysis