Codeforces Round #233 (Div. 2)

#include 
#include 

int n;
char str[55];
__int64 mi[55];

void init() {
	mi[0] = 1;
	for (int i = 1; i <= 50; i++)
		mi[i] = mi[i - 1] * 2;
}

int main() {
	init();
	scanf("%d%s", &n, str);
	__int64 ans = 0;
	for (int i = 0; i < n; i++)
		if (str[i] == 'B')
			ans += mi[i];
	printf("%I64d\n", ans);
	return 0;
}

#include 
#include 
#define max(a,b) ((a)>(b)?(a):(b))
__int64 a, b;

__int64 cal(int num) {
	__int64 ans = 0;
	ans += num - 1 + (a - (num - 1)) * (a - (num - 1));
	__int64 k = b / (num + 1) + 1;
	__int64 kk = k * (num + 1) - b;
	ans -= (kk * (k - 1) * (k - 1) + (num + 1 - kk) * k * k);
	return ans;
}

void print(int x) {
	int k = b / x + 1;
	int kk = k * x - b;
	int kkk = x - kk;
	int sb = x - 2;
	int sbb = 1;
	while (kk) {
		for (int i = 0; i < k - 1; i++) {
			printf("x");
		}
		kk--;
		if (sb != 0) {
			printf("o");
			sb--;
		}
		else if (sbb != 0) {
			for (int i = 0; i < a - (x - 2); i++)
				printf("o");
			sbb--;
		}
	}
	while (kkk) {
		for (int i = 0; i < k; i++) {
			printf("x");
		}
		kkk--;
		if (sb != 0) {
			printf("o");
			sb--;
		}
		else if (sbb != 0) {
			for (int i = 0; i < a - (x - 2); i++)
				printf("o");
			sbb--;
		}
	}
	printf("\n");
}
int main() {
	__int64 ans = -10000000000000000;
	int ansv;
	scanf("%I64d%I64d", &a, &b);
	if (b == 0) {
		printf("%I64d\n", a * a);
		for (int i = 0; i < a; i++)
			printf("o");
		printf("\n");
		return 0;
	}
	if (a == 0) {
		printf("%I64d\n", -b * b);
		for (int i = 0; i < b; i++)
			printf("x");
		printf("\n");
		return 0;
	}
	for (int i = 1; i <= a; i++) {
		__int64 t = cal(i);
		if (t > ans) {
			ans = t;
			ansv = i + 1;
		}
	}
	printf("%I64d\n", ans);
	print(ansv);
	return 0;
}

#include 
#include 

const int N = 2005;
int n, m, r, c, rv[N], cv[N], i, j;
double dp[N][N];

int main() {
	scanf("%d%d", &n, &m);
	r = c = n;
	int a, b;
	while (m--) {
		scanf("%d%d", &a, &b);
		if (rv[a] == 0) r--;
		if (cv[b] == 0) c--;
		rv[a] = 1; cv[b] = 1;
	}
	for (i = 1; i <= n; i++) {
		dp[i][0] = dp[i - 1][0] + (double)n/i;
		dp[0][i] = dp[0][i - 1] + (double)n/i;
	}
	for (i = 1; i <= n; i++) {
		for (j = 1; j <= n; j++) {
			dp[i][j] = n * n;
			dp[i][j] += dp[i - 1][j - 1] * i * j;
			dp[i][j] += dp[i - 1][j] * i * (n - j);
			dp[i][j] += dp[i][j - 1] * (n - i) * j;
			dp[i][j] /= (n * n - (n - i) * (n - j));
		}
	}
	printf("%.10lf\n", dp[r][c]);
	return 0;
}

#include 
#include 

int n, i;
int main() {
	scanf("%d", &n);
	if (n == 5)
		printf("1 2 3\n1 3 3\n2 4 2\n4 5 1\n3 4\n3 5\n");
    else {
		for (i = 1; i <= n/2; i++) printf("%d %d 1\n", i, i+n/2);
		for (i = n/2 + 1; i <= n - 1; i++) printf("%d %d %d\n", i, i + 1, 2 * (i - n/2) - 1);
		for (i = 1; i <= n/2 - 1; i++) printf("%d %d\n", i, i +1);
		printf("1 3\n");
	}
	return 0;
}