*[hackerrank]ACM ICPC Team

https://www.hackerrank.com/contests/w6/challenges/acm-icpc-team

这道题在contest的时候数据量改小过，原来的数据量需要进行优化才能过。参考了：http://chasethered.com/2014/07/hackerrank-weekly-challenge-6-problem-1/

首先是转化成int32的数组，然后N^N的复杂度两两比较求bit数。求bit中1的个数有几种做法：

- x & (x - 1)
- Hamming weight的经典求法，基于树状累加：http://en.wikipedia.org/wiki/Hamming_weight
- 内存足够大可以查表得；

#include <iostream>

#include <vector>

#include <string>

using namespace std;



int bitCount(unsigned int u) {

   unsigned int uCount;

 

   uCount = u - ((u >> 1) & 033333333333) - ((u >> 2) & 011111111111);

   return ((uCount + (uCount >> 3)) & 030707070707) % 63;

}



int main() {

	int N;

	int M;

	cin >> N >> M;

	vector<vector<int>> bm(N);

	int len = (M - 1) % 32 + 1;

	for (int i = 0; i < N; i++) {

		bm[i].resize(len);

	}

	for (int i = 0; i < N; i++) {

		string s;

		cin >> s;

		int k = -1;

		for (int j = 0; j < M; j++) {

			if (j % 32 == 0)

				k++;

			bm[i][k] *= 2;

			bm[i][k] += (int) (s[j] - '0');

		}

	}

	int topicCount = 0;

	int teamCount = 0;

	for (int i = 0; i < N; i++) {

		for (int j = i + 1; j < N; j++) {

			int local = 0;

			for (int k = 0; k < len; k++) {

				unsigned int tmp = bm[i][k] | bm[j][k];

				int count = bitCount(tmp);

				local += count;

			}

			if (local > topicCount) {

				topicCount = local;

				teamCount = 1;

			} else if (local == topicCount) {

				teamCount++;

			}

		}

	}

	cout << topicCount << endl;

	cout << teamCount << endl;

	return 0;

}