HDU 1542 Atlantis (rectangular area and)

HDU 1542 Atlanta

Question Link

Give some rectangles, calculate the area and

Idea: using scanning lines, because there are not many rectangles in this question, you can simply scan them by force. If the data is big, you need to use the line segment tree.

Code:

#include <cstdio>#include <cstring>#include <cmath>#include <algorithm>using namespace std;const int N = 205;const int M = 100005;const double eps = 1e-8;int n, vis[N], hn;double hash[N];struct Line {double l, r, y;int flag;Line() {}Line(double l, double r, double y, int flag) {this->l = l;this->r = r;this->y = y;this->flag = flag;}} line[N];bool cmp(Line a, Line b) {return a.y < b.y;}int get(double x) {return lower_bound(hash, hash + hn, x) - hash;}int main() {int cas = 0;while (~scanf("%d", &n) && n) {double x1, x2, y1, y2; hn = 0;memset(vis, 0, sizeof(vis));for (int i = 0; i < n; i++) {scanf("%lf%lf%lf%lf", &x1, &y1, &x2, &y2);line[i * 2] = Line(x1, x2, y1, 1);line[i * 2 + 1] = Line(x1, x2, y2, -1);hash[hn++] = x1; hash[hn++] = x2;}n *= 2;sort(line, line + n, cmp);sort(hash, hash + hn);hn = 1;for (int i = 1; i < n; i++) {if (fabs(hash[i] - hash[i - 1]) < eps) continue;hash[hn++] = hash[i];}double ans = 0;for (int i = 0; i < n; i++) {int l = get(line[i].l), r = get(line[i].r);double len = 0;for (int j = 0; j < hn - 1; j++) if (vis[j] > 0) len += (hash[j + 1] - hash[j]);if (i) ans += len * (line[i].y - line[i - 1].y);for (int j = l; j < r; j++) vis[j] += line[i].flag;}printf("Test case #%d\n", ++cas);printf("Total explored area: %.2lf\n\n", ans);}return 0;}

HDU 1542 Atlantis (rectangular area and)