HDOJ 5024 Wang Xifeng's Little Plot

#include<cstdio>
#include<cstring>
#include<vector>
#include<algorithm>
#include<iostream>
#include<string>
#include<queue>
#include<stack>
#include<cmath>
#include<cctype>
#include<map>
#include<set>
#include<sstream>
using namespace std;
const int OO=(1<<30);
typedef long long LL;
struct Path{
    int from;
    int len;
    int to;
    int dir;///路径的走向
    Path(int from,int to,int len,int dir):from(from),to(to),len(len),dir(dir){}
    bool operator<(const Path& rhs)const{
    if(from<rhs.from)return true;
    return false;
    }
};
vector<Path>paths;

const int maxn=110;
const int dr[]={-1,1,0,0,1,-1,1,-1};///北,南,西,东,东南,东北,西南,西北
const int dc[]={0,0,-1,1,1,1,-1,-1};
bool is_rec(int i,int j){
    if(i>j)swap(i,j);
    if( (i==0 || i==1) && (j==2 || j==3) )return true;
    if( (i==2 || i==3) && (j==1 || j==0) )return true;
    if( (i==4 || i==7) && (j==5 || j==6) )return true;
    if( (i==5 || i==6) && (j==4 || j==7) )return true;
    return false;
}

char net[maxn][maxn];
int R;

int main(){
    while(scanf("%d",&R) && R){
        for(int i=0;i<R;i++)
            scanf("%s",net[i]);
        paths.clear();int ans=-OO;
        for(int from=0;from<R*R;from++)///枚举每条路径的起点
            if(net[from/R][from%R]=='.')
                for(int dir=0;dir<8;dir++){///枚举每条路径的方向;
                    int len=0;
                    int r=from/R;///起点的行数
                    int c=from%R;///起点的列数
                    while(r+dr[dir]>=0 && r+dr[dir]<R && c+dc[dir]>=0 && c+dc[dir]<R && net[ r+dr[dir] ][ c+dc[dir] ]=='.'){
                        len++;
                        r=r+dr[dir];
                        c=c+dc[dir];
                    }
                    int to=r*R+c;
                    if(to!=from){ paths.push_back(Path(from,to,len+1,dir) );ans=max(ans,len+1);}
                }
                int size=paths.size();
                sort(paths.begin(),paths.end());      
                for(int i=0;i<size;i++){
                    if(!binary_search(paths.begin(),paths.end(),paths[i]))continue;
                    int low=lower_bound(paths.begin(),paths.end(),paths[i])-paths.begin();
                    int high=upper_bound(paths.begin(),paths.end(),paths[i])-paths.begin()-1;
                    for(int j=low;j<high;j++)///道路是有向的
                        if(is_rec(paths[i].dir,paths[j].dir)){
                            ans=max(ans,paths[i].len+paths[j].len-1);
                        }
                }
                cout<<ans<<endl;
    }
    return 0;
}