HDU 5033 Building（北京网络赛B题）

来源：互联网发布：图片的相似度算法编辑：程序博客网时间：2024/06/09 19:49

HDU 5033 Building

题目链接

思路：利用单调栈维护建筑建的斜线，保持斜率单调性，然后可以把查询当成高度为0的建筑，和建筑和在一起考虑，从左往右和从右往左各扫一遍即可

代码：

#include <cstdio>#include <cstring>#include <queue>#include <cmath>#include <algorithm>using namespace std;const int N = 200005;const double pi = acos(-1.0);const double eps = 1e-8;int t, n, q;struct Build {double x, h;bool isq;double s[2];int id;} b[N], Q[N];bool cmp(Build a, Build b) {return a.x < b.x;}bool cmpid(Build a, Build b) {return a.id < b.id;}double cal(Build a, Build b) {double dx = fabs(b.x - a.x);double dy = b.h - a.h;return dy / dx;}int main() {int cas = 0;scanf("%d", &t);while (t--) {scanf("%d", &n);for (int i = 0; i < n; i++) {scanf("%lf%lf", &b[i].x, &b[i].h);b[i].isq = false;b[i].id = i;}scanf("%d", &q);for (int i = n; i < n + q; i++) {scanf("%lf", &b[i].x);b[i].h = 0;b[i].isq = true;b[i].id = i;}n += q;sort(b, b + n, cmp);Q[0] = b[0];int top = 0;int u = 0;for (int i = 1; i < n; i++) {if (b[i].isq == false) {while (top && cal(b[i], Q[top]) < cal(Q[top], Q[top - 1]))top--;Q[++top] = b[i];} else {int tmp = top;while (tmp && cal(b[i], Q[tmp]) < cal(b[i], Q[tmp - 1]))tmp--;b[i].s[u] = cal(b[i], Q[tmp]);}}reverse(b, b + n);Q[0] = b[0];top = 0;u = 1;for (int i = 1; i < n; i++) {if (b[i].isq == false) {while (top && cal(b[i], Q[top]) < cal(Q[top], Q[top - 1]))top--;Q[++top] = b[i];} else {int tmp = top;while (tmp && cal(b[i], Q[tmp]) < cal(b[i], Q[tmp - 1]))tmp--;b[i].s[u] = cal(b[i], Q[tmp]);}}sort(b, b + n, cmpid);printf("Case #%d:\n", ++cas);for (int i = 0; i < n; i++) {if (b[i].isq) {double ans = pi - atan(b[i].s[0]) - atan(b[i].s[1]);ans = ans / pi * 180;printf("%.10lf\n", ans);}}}return 0;}

1 0