There are several ancient Greek texts that contain descriptions of the fabled island Atlantis. Some of these texts even include maps of parts of the island. But unfortunately, these maps describe different regions of Atlantis. Your friend Bill has to know the total area for which maps exist. You (unwisely) volunteered to write a program that calculates this quantity.

The input file consists of several test cases. Each test case starts with a line containing a single integer n (1<=n<=100) of available maps. The n following lines describe one map each. Each of these lines contains four numbers x1;y1;x2;y2 (0<=x1<x2<=100000;0<=y1<y2<=100000), not necessarily integers. The values (x1; y1) and (x2;y2) are the coordinates of the top-left resp. bottom-right corner of the mapped area.

The input file is terminated by a line containing a single 0. Don’t process it.

For each test case, your program should output one section. The first line of each section must be “Test case #k”, where k is the number of the test case (starting with 1). The second one must be “Total explored area: a”, where a is the total explored area (i.e. the area of the union of all rectangles in this test case), printed exact to two digits to the right of the decimal point.

Output a blank line after each test case.

2
10 10 20 20
15 15 25 25.5
0

Test case #1
Total explored area: 180.00 

Mid-Central European Regional Contest 2000

version 1:

/*=============================================================================
#
#      Author: liangshu - cbam 
#
#      QQ : 756029571 
#
#      School : 哈尔滨理工大学 
#
#      Last modified: 2015-08-11 12:30
#
#     Filename: A.cpp
#
#     Description: 
#        The people who are crazy enough to think they can change the world, are the ones who do ! 
=============================================================================*/
#

#include<iostream>    
#include<sstream>    
#include<algorithm>    
#include<cstdio>    
#include<string.h>    
#include<cctype>    
#include<string>    
#include<cmath>    
#include<vector>    
#include<stack>    
#include<queue>    
#include<map>    
#include<set>    
using namespace std;

const int INF = 2024;
struct line {
    double s, e, y, mark;
    line(double s, double e, double y, double ma):s(s),e(e),y(y), mark(ma){}
    bool friend operator < (line a, line  b){
        return a.y < b.y;
    }
};

struct Tree{
    int cover;
    int lft,rht;double sum;
}tree[INF<<2];

vector<double>X;
vector<line>L;
map<double, int>h;

void create(int root, int left, int right){
    tree[root].lft = left;
    tree[root].rht = right;
    tree[root].sum = 0;
    if(left + 1 != right){
        int mid = (left + right)/2;
        create(root<<1, left, mid);
        create(root<<1|1, mid, right);
    }
    return ;
}

void update(int root, int val, int left, int right){
    if(tree[root].lft >= left && tree[root].rht <= right){
        tree[root].cover += val;
        if(tree[root].cover){
            tree[root].sum =  X[tree[root].rht] - X[tree[root].lft];return ;
        }
        else{
            tree[root].sum = tree[root<<1].sum + tree[root<<1|1].sum;
            return ;
        }
    }
    if(tree[root].lft == tree[root].rht)return ;
    int mid = (tree[root].lft + tree[root].rht)/2;
    if(left < mid){
        update(root <<1, val, left, right);
    }
    if(right >= mid){
        update(root<<1|1,val,left, right);
    }
    if(!tree[root].cover)
    tree[root].sum = tree[root<<1].sum + tree[root<<1|1].sum;
}

int main(){
    int n,cs = 1;
    while(~scanf("%d", &n)&&n){
        h.clear();L.clear();X.clear();
        double x1, y1, x2, y2;
        for(int i = 1; i <= n; i++){
            scanf("%lf%lf%lf%lf",&x1, &y1, &x2, &y2);
            L.push_back(line(x1, x2, y1, 1));
            L.push_back(line(x1, x2, y2, -1));
            X.push_back(x1);X.push_back(x2);
        }
        sort(X.begin(), X.end());
        sort(L.begin(), L.end());
       X.erase(unique(X.begin(),X.end()), X.end());
       for(int i = 0; i < X.size(); i++){
           h[X[i]] = i;
       }
       create(1, 0, X.size() - 1);
       double ans = 0;int i;
       for( i = 0; i < L.size() - 1; i++){
           update(1, L[i].mark, h[L[i].s], h[L[i].e]);
               ans += (L[i + 1].y - L[i].y) * tree[1].sum;
       }
           update(1, L[i].mark, h[L[i].s], h[L[i].e]);
       printf("Test case #%d\nTotal explored area: %.2lf\n\n",cs++ , ans);
    }
}

version 2 :

/*=============================================================================
#
#      Author: liangshu - cbam 
#
#      QQ : 756029571 
#
#      School : 哈尔滨理工大学 
#
#      Last modified: 2015-08-11 12:50
#
#     Filename: A.cpp
#
#     Description: 
#        The people who are crazy enough to think they can change the world, are the ones who do ! 
=============================================================================*/
#


#include<iostream>
#include<sstream>
#include<algorithm>
#include<cstdio>
#include<string.h>
#include<cctype>
#include<string>
#include<cmath>
#include<vector>
#include<stack>
#include<queue>
#include<map>
#include<set>
using namespace std;
const int INF = 2222;

struct line
{
    double s, e, y, mark;
} L[INF];

double sum[INF<<2];
int cnt[INF<<2];
vector<double>dict;

bool cmp(line a, line b)
{
    return a.y < b.y;
}

void pushup(int rt, int l, int r)
{
    if(cnt[rt])
    {
        sum [rt] = dict[r + 1] - dict[l] ;
    }
    else
        sum[rt] = sum[rt<<1] + sum[rt<<1|1];
}
int  bin(double k, int len)
{
    int l = 0, r = len - 1;
    while (l <= r)
    {
        int mid = (l + r)>>1;
        if(dict[mid] == k)return mid;
        else if(dict[mid] > k)r = mid - 1;
        else l = mid + 1;
    }
    return -1;
}
void  update(int rt, int L, int R, int l ,int r, int val)
{
    if(L <= l && r <= R)
    {
        cnt[rt] += val;
        pushup(rt, l, r);
        return ;
    }
    int mid = (l + r)>>1;
    if(L <= mid)update(rt<<1, L, R, l , mid, val);
    if(R > mid)update(rt<<1|1,L, R, mid + 1, r, val);
    pushup(rt,l, r);
}

int main()
{
    int n,cs = 1;
    while(scanf("%d", &n) != EOF && n)
    {
        memset(sum, 0, sizeof(sum));
        int t = 0;
        for(int i = 1; i <= n; i++)
        {
            double x1,y1,x2,y2;
            scanf("%lf%lf%lf%lf", &x1, &y1, &x2, &y2);
            dict.push_back (x1);
            L[t].s = x1;
            L[t].e = x2;
            L[t].y = y1;
            L[t++].mark = 1;
            dict.push_back(x2);
            L[t].s = x1;
            L[t].e = x2;
            L[t].y = y2;
            L[t++].mark = -1 ;
        }
        sort(L , L + t, cmp);
        sort(dict .begin(), dict.end());
        dict.erase (unique(dict.begin(), dict.end()), dict.end());
        double ans = 0;
        for(int i = 0; i < t ; i ++ )
        {
            int l = bin(L[i].s, dict.size());
            int r = bin(L[i].e, dict.size()) - 1;
            if(l <= r)
                update(1, l, r, 0, dict.size() - 1, L[i].mark);
            ans += sum[1] * (L[i + 1].y - L[i].y);
        }
        printf("Test case #%d\nTotal explored area: %.2lf\n\n",cs++ , ans);
    }
    return 0 ;
}