2271.cpp

这是哈尔滨工业大学acmOJ的源代码

/*  This Code is Submitted by wywcgs for Problem 2271 on 2006-06-13 at 22:56:10 */ 
#include <cstdio>
#include <cmath>
#include <algorithm>
using namespace std;

const int BN = 256;
const int DIR[][2] = { { 0, 0 }, { 0, 1 }, { 1, 0 }, { 1, 1 } };
const double SQRT_3 = sqrt(3.0);

int main()
{
	int n, i, j, k;
	bool point[BN][BN];
	
	while(scanf("%d", &n) != EOF) {
		memset(point, false, sizeof(point));
		for(i = 0; i < n; i++) {
			int x, y; scanf("%d %d", &x, &y);
			point[x+BN/2][y+BN/2] = true;
		}
		double area = 0;
		for(i = 0; i < BN-1; i++)
			for(j = 0; j < BN-1; j++) {
				int st = 0, pn = 0;
				for(k = 0; k < 4; k++) {
					int x = i+DIR[k][0], y = j+DIR[k][1];
					if(point[x][y]) { st |= 1 << k; pn++; }
				}
				double da;
				if(pn == 0) da = 0;
				else if(pn == 1) da = M_PI/4;
				else if((st&6) == 6 || (st&9) == 9) da = 1;
				else da = SQRT_3/4+M_PI/6;
				if(fabs(da) > 1e-4)
				area += da;
			}
		printf("%.2lf\n", area);
	}
	
	return 0;
}