HDU1542

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=1542

矩形面积并

对于浮点数的离散化，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 | 1const 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;}