hdu 5033 单调栈 ****

看出来是单调栈维护斜率，但是不会写，2333，原来是和询问放在一起的

 #include <iostream>
 #include <cstdio>
 #include <cstring>
 #include <algorithm>
 #include <queue>
 #include <cmath>
 typedef __int64 ll;
 using namespace std;

 const double PI = acos(-1.0);
 const int maxn = ;

 struct Node {
     int x, h;
     bool operator <(const Node &a)const {
         return x < a.x;
     }
 } node[maxn<<], stk[maxn<<];
 double ans[maxn];
 int n, q;

 int check(Node &a, Node &b, Node c) {
     if (c.h <= )
         c.h = ;
     return (ll)(a.h - c.h) * (c.x - b.x) >= (ll)(b.h - c.h) * (c.x - a.x);
 }

 double getAngle(Node a, Node b) {
     return atan((double)(b.x-a.x)/(double)(a.h));
 }

 void cal() {
     int head = ;
     for (int i = ; i < n+q; i++) {
         if (node[i].h <= ) {
             while (head >=  && check(stk[head-], stk[head-], node[i]))
                 head--;
             ans[-node[i].h] += getAngle(stk[head-], node[i]);
         }
         else {
             while (head && stk[head-].h <= node[i].h)
                 head--;
             while (head >=  && check(stk[head-], stk[head-], node[i]))
                 head--;
             stk[head++] = node[i];
         }
     }
 }

 int main() {
     int t, cas = ;
     scanf("%d", &t);
     while (t--) {
         scanf("%d", &n);
         for (int i = ; i < n; i++)
             scanf("%d%d", &node[i].x, &node[i].h);
         scanf("%d", &q);
         for (int i = ; i < q; i++) {
             scanf("%d", &node[i+n].x);
             node[i+n].h = -i;
         }

         memset(ans, , sizeof(ans));
         sort(node, node+n+q);

         cal();

         reverse(node, node+n+q);
         for (int i = ; i < n+q; i++)
             node[i].x =  - node[i].x;

         cal();

         printf("Case #%d:\n", cas++);
         for (int i = ; i < q; i++)
             printf("%.10lf\n", ans[i] * 180.0 / PI);
     }
     return ;
 }