还是先离散化坐标，然后用线段树扫描线
其中sum代表被覆盖过一次的长度，sum2代表被覆盖过2次及以上的长度。
然后注意pushup操作比较麻烦。
/*
ID: sdj22251
PROG: subset
LANG: C++
*/
#include <iostream>
#include <vector>
#include <list>
#include <map>
#include <set>
#include <deque>
#include <queue>
#include <stack>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <cmath>
#include <ctime>
#define MAXN 2222
#define MAXM 164444
#define INF 100000000
#define eps 1e-7
#define L(X) X<<1
#define R(X) X<<1|1
using namespace std;struct node
{int left, right, mid;int cnt;double sum, sum2;
}tree[4 * 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;}
}seg[2 * MAXN];
double x[MAXN];
int ct ;
void up(int C)
{if(tree[C].cnt > 1){tree[C].sum = 0.0;tree[C].sum2 = x[tree[C].right + 1] - x[tree[C].left];}else if(tree[C].cnt == 1){if(tree[C].left == tree[C].right){tree[C].sum = x[tree[C].right + 1] - x[tree[C].left]; tree[C].sum2 = 0;}else{tree[C].sum2 = tree[L(C)].sum + tree[L(C)].sum2 + tree[R(C)].sum + tree[R(C)].sum2;tree[C].sum = x[tree[C].right + 1] - x[tree[C].left] - tree[C].sum2;}}else{if(tree[C].left == tree[C].right) tree[C].sum = tree[C].sum2 = 0.0;else{tree[C].sum = tree[L(C)].sum + tree[R(C)].sum;tree[C].sum2 = tree[L(C)].sum2 + tree[R(C)].sum2;}}
}void make_tree(int s, int e, int C)
{tree[C].left = s;tree[C].right = e;tree[C].mid = (s + e) >> 1;tree[C].cnt = 0;tree[C].sum = 0.0;tree[C].sum2 = 0.0;if(s == e) return;make_tree(s, tree[C].mid, L(C));make_tree(tree[C].mid + 1, e, R(C));
}void update(int s, int e, int v, int C)
{if(tree[C].left >= s && tree[C].right <= e){tree[C].cnt += v;up(C);return;}if(tree[C].mid >= s) update(s, e, v, L(C));if(tree[C].mid < e) update(s, e, v, R(C));up(C);
}int bin(double v, int bound)
{int low = 0, high = bound - 1;while(low <= high){int mid = (low + high) >> 1;if(x[mid] == v) return mid;if(x[mid] < v) low = mid + 1;else high = mid - 1;}return -1;
}int main()
{int T, n;scanf("%d", &T);while(T--){ct = 0;scanf("%d", &n);int m = 0;double a, b, c, d;while(n--){scanf("%lf%lf%lf%lf", &a, &b, &c, &d);x[m] = a;seg[m++] = Seg(a, c, b, 1);x[m] = c;seg[m++] = Seg(a, c, d, -1);}sort(x, x + m);sort(seg, seg + m);int k = unique(x, x + m) - x;make_tree(0, k - 1, 1);double ans = 0;for(int i = 0; i < m - 1; i ++){int l = bin(seg[i].l, k);int r = bin(seg[i].r, k) - 1;update(l, r, seg[i].s, 1);ans += tree[1].sum2 * (seg[i + 1].h - seg[i].h);}printf("%.2f\n", ans);}return 0;
}