juruo求助

#include<iostream>
#include<algorithm>
#include<cstring>

using namespace std;
int l, w, n;
struct Node{
    int x;
    int y;
};
Node point[5010];

bool cmp(Node x, Node y){
    return x.x<y.x;
}

bool cmp2(Node x, Node y){
    return x.y<y.y;
}

int main(){
    cin >> l >> w >> n;
    for(int i=1;i<=n;i++){
        cin >> point[i].x >> point[i].y;
    }
    point[n+1].x=0;
    point[n+1].y=0;
    point[n+2].x=l;
    point[n+2].y=0;
    point[n+3].x=0;
    point[n+3].y=w;
    point[n+4].x=l;
    point[n+4].y=w;
    int ans=0;
    n+=4;
    sort(point+1, point+n+1, cmp);
    int left=0, right=l, down=0, up=w;
    for(int i=1;i<=n;i++){
        left=point[i].x;
        right=l;
        up=w;
        down=0;
        for(int j=i+1;j<=n;j++){
            ans=max(ans, (point[j].x-left)*(up-down));
            if(point[i].y>point[j].y) down=max(down, point[i].y);
            if(point[i].y<point[j].y) up=min(up, point[i].y);
            if(point[j].y==point[i].y) break;
        }
    }
    for(int i=n;i>0;i--){
        left=0;
        right=point[i].x;
        up=w;
        down=0;
        for(int j=i+1;j>0;j--){
            ans=max(ans, (right-point[j].x)*(up-down));
            if(point[i].y>point[j].y) down=max(down, point[i].y);
            if(point[i].y<point[j].y) up=min(up, point[i].y);
            if(point[j].y==point[i].y) break;
        }
    }
    sort(point+1, point+n+1, cmp2);
    down=0;
    up=point[1].y;
    for(int i=2;i<=n;i++){
        ans=max(ans, l*(up-down));
        down=up;
        up=point[i].y;
    }
    cout << ans << endl;
    return 0;
}