[CODEVS 3044] 矩形面积求并

#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;

const int maxn = 100 + 10;

struct Matrix {
double x1, y1, x2, y2;
} matrixs[maxn];

double x[maxn<<1], y[maxn<<1];
bool covered[maxn<<1][maxn<<1];

int main() {
int n;
while(scanf("%d", &n) == 1) {
if(n == 0) break;
for(int i = 0; i < n; i++) {
double x1, y1, x2, y2;
scanf("%lf%lf%lf%lf", &x1, &y1, &x2, &y2);
matrixs[i] = (Matrix) {x1, y1, x2, y2};
x[i<<1] = x1;
y[i<<1] = y1;
x[(i<<1) ^ 1] = x2;
y[(i<<1) ^ 1] = y2;
}
sort(x, x + 2*n);
sort(y, y + 2*n);

// 以左下点的坐标作为格子的编号.
memset(covered, 0, sizeof(covered));
for(int cur = 0; cur < n; cur++) {
int s_x, s_y, t_x, t_y;
Matrix& M = matrixs[cur];
for(s_x = 0; x[s_x] < M.x1; s_x++);
for(s_y = 0; y[s_y] < M.y1; s_y++);
for(t_x = s_x; x[t_x] < M.x2; t_x++);
for(t_y = s_y; y[t_y] < M.y2; t_y++);
// cover
for(int i = s_x; i < t_x; i++)
for(int j = s_y; j < t_y; j++)
covered[i][j] = 1;
}

double ans = 0.00;
for(int i = 0; i < 2*n - 1; i++)
for(int j = 0; j < 2*n - 1; j++)
if(covered[i][j]) ans += (x[i + 1]-x[i]) * (y[j + 1]-y[j]);
printf("%.2lf\n", ans);
}
return 0;
}