【POJ 1151】 Altlantis

【题目链接】
【算法】
线段树扫描线
推荐一篇比较容易理解的线段树扫描线的文章： https://blog.csdn.net/u013480600/article/details/22548393
【代码】
注意此题输出格式若使用"%.2lf"会离奇Wrong Answer,要改为"%.2f"
#include <algorithm>
#include <bitset>
#include <cctype>
#include <cerrno>
#include <clocale>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <limits>
#include <list>
#include <map>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <utility>
#include <vector>
#include <cwchar>
#include <cwctype>
#include <stack>
#include <limits.h>
using namespace std;
#define MAXN 110

int i,n,l1,l2,l,L,R,TC;
double xa,ya,xb,yb,area;
double a[MAXN*2],x[MAXN*2],arr[MAXN*2];

struct info {
        double l,r,h,opt;
} y[MAXN*2];

struct SegmentTree {
        struct Node {
                int l,r,c;
                double m;
        } Tree[MAXN*4];
        inline void build(int index,int l,int r) {
                int mid;
                Tree[index].l = l;
                Tree[index].r = r;
                Tree[index].m = 0.0;
                Tree[index].c = 0;
                if (l == r) return;
                mid = (l + r) >> 1;
                build(index<<1,l,mid);
                build(index<<1|1,mid+1,r);
        }
        inline void update(int index) {
                if (Tree[index].c > 0) Tree[index].m = arr[Tree[index].r+1] - arr[Tree[index].l];
                else if (Tree[index].l == Tree[index].r) Tree[index].m = 0;
                else Tree[index].m = Tree[index<<1].m + Tree[index<<1|1].m;
        }
        inline void add(int index,int l,int r,int val) {
                int mid;
                if (Tree[index].l == l && Tree[index].r == r) {
                        Tree[index].c += val;
                        update(index);
                        return;
                }
                mid = (Tree[index].l + Tree[index].r) >> 1;
                if (mid >= r) add(index<<1,l,r,val);
                else if (mid + 1 <= l) add(index<<1|1,l,r,val);
                else {
                        add(index<<1,l,mid,val);
                        add(index<<1|1,mid+1,r,val);
                }
                update(index);
        }
        inline double query() {
                return Tree[1].m;
        }
} T;

bool cmp(info a,info b) { return a.h > b.h; }

int main() {
        
        while (scanf("%d",&n) != EOF && n) {
                l = l1 = l2 = 0;
                for (i = 1; i <= n; i++) {
                        scanf("%lf%lf%lf%lf",&xa,&ya,&xb,&yb);
                        x[++l1] = xa;
                        x[++l1] = xb;
                        y[++l2] = (info){xa,xb,ya,-1};
                        y[++l2] = (info){xa,xb,yb,1};
                }    
                sort(x+1,x+l1+1);
                x[0] = -1;
                for (i = 1; i <= l1; i++) {
                        if (x[i] != x[i-1])
                                arr[++l] = x[i];
                }
                T.build(1,1,l-1);
                sort(y+1,y+l2+1,cmp);
                area = 0.0;
                for (i = 1; i < l2; i++) {
                        L = lower_bound(arr+1,arr+l+1,y[i].l) - arr;
                        R = lower_bound(arr+1,arr+l+1,y[i].r) - arr - 1;
                        T.add(1,L,R,y[i].opt);
                        area += T.query() * (y[i].h - y[i+1].h);
                }
                printf("Test case #%d
Total explored area: %.2f

",++TC,area);
        }
        
        return 0;
    
}