HDU1542

題目鏈接：http://acm.hdu.edu.cn/showproblem.php?pid=1542

矩形面積並

對於浮點數的離散化，真心看不懂啊……

#include <cstdio>
#include <cstring>
#include <cctype>
#include <algorithm>
using namespace std;

#define lson l , m , rt << 1
#define rson m + 1 , r , rt << 1 | 1

const int maxn = 2222;
int cnt[maxn << 2];
double sum[maxn << 2];
double X[maxn];

struct Seg
{
	double h , l , r;
	int s;
	Seg(){}
	Seg(double a,double b,double c,int d) : l(a) , r(b) , h(c) , s(d) {}
	bool operator < (const Seg &cmp) const
	{
		return h < cmp.h;
	}
}ss[maxn];

void PushUp(int rt,int l,int r)
{
	if (cnt[rt]) sum[rt] = X[r+1] - X[l];
	else if (l == r) sum[rt] = 0;
	else sum[rt] = sum[rt<<1] + sum[rt<<1|1];
}

void update(int L,int R,int c,int l,int r,int rt)
{
	if (L <= l && r <= R)
	{
		cnt[rt] += c;
		PushUp(rt , l , r);
		return ;
	}
	int m = (l + r) >> 1;
	if (L <= m) update(L , R , c , lson);
	if (m < R) update(L , R , c , rson);
	PushUp(rt , l , r);
}

int Bin(double key,int n,double X[])
{
	int l = 0 , r = n - 1;
	while (l <= r)
	{
		int m = (l + r) >> 1;
		if (X[m] == key) return m;
		if (X[m] < key) l = m + 1;
		else r = m - 1;
	}
	return -1;
}

int main()
{
	int n , cas = 1;
	while (~scanf("%d",&n) && n)
	{
		int m = 0;
		while (n --)
		{
			double a , b , c , d;
			scanf("%lf%lf%lf%lf",&a,&b,&c,&d);
			X[m] = a;
			ss[m++] = Seg(a , c , b , 1);
			X[m] = c;
			ss[m++] = Seg(a , c , d , -1);
		}
		sort(X , X + m);
		sort(ss , ss + m);
		int k = unique(X, X+m) - X;
		memset(cnt , 0 , sizeof(cnt));
		memset(sum , 0 , sizeof(sum));
		double ret = 0;
		for (int i = 0 ; i < m - 1 ; i ++)
		{
			int l = Bin(ss[i].l , k , X);
			int r = Bin(ss[i].r , k , X) - 1;
			if (l <= r) update(l , r , ss[i].s , 0 , k - 1, 1);
			ret += sum[1] * (ss[i+1].h - ss[i].h);
		}
		printf("Test case #%d\nTotal explored area: %.2lf\n\n",cas++ , ret);
	}

	return 0;
}