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 = 0; c = getchar(), !isdigit(c); ) if(c == '-') f = 1;
    for(x = 0; isdigit(c); c = getchar()) x = x * 10 + c - '0';
    return f && (x = -x), x;
}
template<typename Q> Q read() {
    static Q x; return read(x);
}

const int N = 5000 + 10;

struct Node {
    int x, y;
    Node(int x = 0, int y = 0) : 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 = 0;
    for(int i = 0; i < n; i++) {
        int U = H, D = 0;
        for(int j = i + 1; 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 = 0; i < n; i++) {
        int x = read<int>(), y = read<int>();
        p[i] = Node(x, y);
    }
    p[n++] = Node(0, 0);
    p[n++] = Node(0, H);
    p[n++] = Node(L, 0);
    p[n++] = Node(L, H);
    
    int ans = 0;
    sort(p, p + n, cmpy);
    for(int i = 1; i < n; i++) {
        ans = max(ans, (p[i].y - p[i-1].y) * L);
    }
    sort(p, p + n, cmpx);
    ans = max(ans, calc());
    for(int i = 0; i < n; i++) p[i].x *= -1;
    reverse(p, p + n);
    printf("%d
", max(ans, calc()));
    
    return 0;
}