[CQOI2013]新Nim游戏

/**

 * Problem:Nim

 * Author:Shun Yao

 * Time:2013.5.28

 * Result:Accepted

 */



#include <cstdio>



void swap(long &x, long &y) {

	x ^= y;

	y ^= x;

	x ^= y;

}



int main() {

	long n, a[100], b[100];

	freopen("nim.in", "r", stdin);

	freopen("nim.out", "w", stdout);

	scanf("%ld", &n);

	for (long i = 0; i < n; ++i) {

		scanf("%ld", a + i);

		b[i] = a[i];

	}

	long now = -1;

	for (long i = 1 << 30; i; i >>= 1) {

		long pos = -1;

		for (long j = now + 1; j < n; ++j)

			if ((a[j] & i) && (pos < 0 || b[j] > b[pos]))

				pos = j;

		if (pos < 0)

			continue;

		++now;

		if (pos != now) {

			swap(a[pos], a[now]);

			swap(b[pos], b[now]);

		}

		for (long j = now + 1; j < n; ++j)

			if (a[j] & i)

				a[j] ^= a[now];

	}

	long long ans = 0;

	for (long i = 0; i < n; ++i)

		if (!a[i])

			ans += (long long)b[i];

	printf("%lld", ans);

	fclose(stdin);

	fclose(stdout);

	return 0;

}

 又有错误: 注意c++ &引用 的用法.