HDOJ 5024 Wang Xifeng's Little Plot

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#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;}
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