【POJ1151】【扫描线+线段树】Atlantis

  1 /*
  2 元稹
  3 《离思五首·其四》
  4 
  5 曾经沧海难为水，除却巫山不是云。
  6 取次花丛懒回顾，半缘修道半缘君。
  7 */
  8 #include <iostream>
  9 #include <cstdio>
 10 #include <algorithm>
 11 #include <cstring>
 12 #include <vector>
 13 #include <utility>
 14 #include <iomanip>
 15 #include <string>
 16 #include <cmath>
 17 #include <queue>
 18 #include <assert.h>
 19 #include <map>
 20 #include <ctime>
 21 #include <cstdlib>
 22 #include <stack>
 23 #define LOCAL
 24 const int MAXN = 10000 + 10;
 25 const int MAXM = 75 + 10;
 26 const int INF = 100000000;
 27 const int SIZE = 450;
 28 const int maxnode =  0x7fffffff + 10;
 29 using namespace std;
 30 struct Line{//扫描线
 31        int flag;//表示是出线还是入线
 32        double x, y1, y2;
 33        
 34        Line (double a, double b, double c, double d){
 35             flag = (int)d;
 36             x = a;
 37             y1 = b;
 38             y2 = c; 
 39        } 
 40        bool operator < (const Line &b)const{
 41             return x < b.x;
 42        };
 43 };
 44 struct Seg_Tree{
 45        struct Node{
 46               int l, r, flag;
 47               double ll, rr, len;
 48        }tree[2000];
 49        vector<double>y, data;
 50        vector<Line>line;
 51        map<double, int>Map;//离散化
 52        
 53        void update(int t, int s, int e, int val){
 54             int l = tree[t].l, r = tree[t].r;
 55             if ((l + 1) == r) {
 56                tree[t].flag += val;
 57                if (tree[t].flag == 0) tree[t].len = 0;
 58                else tree[t].len = tree[t].rr - tree[t].ll;
 59             }
 60             else{
 61                  int mid = (l + r)>>1;
 62                  if (s < mid) update(t << 1, s, e, val);
 63                  if (e > mid) update((t << 1) | 1, s, e, val);
 64                  tree[t].len = tree[t << 1].len + tree[(t << 1) | 1].len;
 65                  
 66             }
 67        }
 68        void build(int t, int l, int r){
 69             tree[t].l = l;
 70             tree[t].r = r;
 71             tree[t].flag = 0;
 72             tree[t].len = 0;
 73             //这两个是代表真实的值 
 74             tree[t].ll = y[l];
 75             tree[t].rr = y[r];
 76             if ((l + 1) == r) return;
 77             //左闭右开 
 78             int mid = (l + r)>>1;
 79             build((t<<1), l, mid);
 80             build((t<<1) | 1, mid, r);
 81        }
 82        void init(){
 83             Map.clear();;
 84             line.clear();
 85             y.clear();
 86             data.clear();
 87        }
 88 }A;
 89 int n;
 90 
 91 void init(){
 92      A.init();
 93      for (int i = 1; i <= n; i++){
 94          double x1, x2, y1, y2;
 95          scanf("%lf%lf%lf%lf", &x1, &y1, &x2, &y2);
 96          A.line.push_back(Line(x1, y1, y2, 1));//1代表入线
 97          A.line.push_back(Line(x2, y1, y2, -1));
 98          A.data.push_back(y1);
 99          A.data.push_back(y2); 
100      }
101      int cnt = 0;//离散化
102      sort(A.data.begin(), A.data.end());
103      for (int i = 0; i < A.data.size(); i++){
104          if (i == 0 || A.data[i] != A.data[i - 1]){
105             A.Map[A.data[i]] = cnt++;
106             A.y.push_back(A.data[i]); 
107          }
108      } 
109 }
110 void work(){
111      sort(A.line.begin(), A.line.end());
112      A.build(1, 0, A.y.size() - 1);
113      double Ans = 0;
114      for (int i = 0; i < A.line.size(); i++){
115          if (i != 0) Ans += (A.line[i].x - A.line[i - 1].x) * A.tree[1].len;
116          A.update(1, A.Map[A.line[i].y1], A.Map[A.line[i].y2], A.line[i].flag);
117      }
118      printf("Total explored area: %.2lf\n\n" , Ans);
119 }
120 
121 int main(){
122     
123     int t = 0;
124     while (scanf("%d", &n) && n){
125           printf("Test case #%d\n", ++t);
126           init();
127           work();
128     }
129     return 0;
130 }