vijos1055 奶牛浴场

挺好的一道题呢

O(n^2)或者O(wh)

 #include<cstdio>
 #include<cstring>
 #include<cstdlib>
 #include<algorithm>
 #include<iostream>

 using namespace std;

 void setIO(const string& s) {
     freopen((s + ".in").c_str(), "r", stdin);
     freopen((s + ".out").c_str(), "w", stdout);
 }

 template<typename Q> Q read(Q& x) {
     static char c, f;
     for(f = ; c = getchar(), !isdigit(c); ) if(c == '-') f = ;
     for(x = ; isdigit(c); c = getchar()) x = x *  + c - '';
     return f && (x = -x), x;
 }
 template<typename Q> Q read() {
     static Q x; return read(x);
 }

 const int N =  + ;

 struct Node {
     int x, y;
     Node(int x = , int y = ) : x(x), y(y) {}
 }p[N];

 bool cmpx(const Node& lhs, const Node& rhs) {
     return lhs.x < rhs.x;
 }

 bool cmpy(const Node& lhs, const Node& rhs) {
     return lhs.y < rhs.y;
 }

 int L, H, n;
 int calc() {
     int ans = ;
     for(int i = ; i < n; i++) {
         int U = H, D = ;
         for(int j = i + ; j < n; j++) {
             ans = max(ans, (p[j].x - p[i].x) * (U - D));
             if(D <= p[j].y && p[j].y <= U) {
                 if(p[j].y > p[i].y) U = p[j].y;
                 else D = p[j].y;
             }
             if(U == D) break;
         }
     }
     return ans;
 }

 int main() {
 #ifdef DEBUG
     freopen("in.txt", "r", stdin);
     freopen("out.txt", "w", stdout);
 #endif

     read(H), read(L), read(n);
     for(int i = ; i < n; i++) {
         int x = read<int>(), y = read<int>();
         p[i] = Node(x, y);
     }
     p[n++] = Node(, );
     p[n++] = Node(, H);
     p[n++] = Node(L, );
     p[n++] = Node(L, H);

     int ans = ;
     sort(p, p + n, cmpy);
     for(int i = ; i < n; i++) {
         ans = max(ans, (p[i].y - p[i-].y) * L);
     }
     sort(p, p + n, cmpx);
     ans = max(ans, calc());
     for(int i = ; i < n; i++) p[i].x *= -;
     reverse(p, p + n);
     printf("%d\n", max(ans, calc()));

     return ;
 }