codeforce 8A-8C

8A用string.find即可，我比较sb的以为string.rfind()和reversestring.find()是一样的，怎么都过不去，被打击透了。

8B开始想的太简单，以为就判断终点是否在中途访问过即可。lur这种情况明显不符合，然后改成bfs，好久没写竟然忘记标记以访问过，搞的mle咯，想了半天才记起来这点...

8C 弱鸡又见dp，无从下手，看了看别人的代码，都说是状态dp，然后拿东西顺序无关，这得好好理解下咯。照例贴大牛代码琢磨...

#include<iostream>
#include<string>
using namespace std;
int main()
{
    string ostr,str1,str2;
    bool ff=false,bf=false;

    cin>>ostr>>str1>>str2;
    unsigned int s;
    if((s=ostr.find(str1))!=string::npos&&ostr.rfind(str2)>(s+str1.length()-1))
        ff=true;
    unsigned int ss;
    string bostr(ostr.rbegin(),ostr.rend());
    if((s=bostr.find(str1))!=string::npos&&bostr.find(str2,s+str1.length())!=-1)
        bf=true;

    if(ff&&bf)
        cout<<"both"<<endl;
    else if(ff&&!bf)
        cout<<"forward"<<endl;
    else if(!ff&&bf)
        cout<<"backward"<<endl;
    else
        cout<<"fantasy"<<endl;

    return 0;
}

#include<iostream>
#include<deque>
using namespace std;
int  robotmap[201][201];


int main()
{
    char str[110]={0};
    cin>>str;
    int lc=0,rc=0,uc=0,dc=0;
    int x=100,y=100;
    for(int i=0;i<strlen(str);i++)
    {
        if(str[i]=='L')
            lc++;
        if(str[i]=='R')
            rc++;
        if(str[i]=='U')
            uc++;
        if(str[i]=='D')
            dc++;
    }
    if(lc==rc&&rc==dc&&dc==uc)
    {
        cout<<"BUG"<<endl;
        return 0;
    }
    else
    {
        robotmap[100][100]=1;
        
        for(int i=0;i<strlen(str);i++)
        {
        if(str[i]=='L')
            x--;
        if(str[i]=='R')
            x++;
        if(str[i]=='U')
            y--;
        if(str[i]=='D')
            y++;

        if(robotmap[x][y]==1)
            {
            cout<<"BUG"<<endl;
            return 0;
            }
        robotmap[x][y]=1;
        }
    }
    struct xy
    {
        int x,y;
        xy(int tx,int ty):x(tx),y(ty){}
        xy(){}
    };
    deque<pair<xy,int> >deq;
    deq.push_back(make_pair(xy(100,100),0));
    pair<xy,int> var;
    int tx,ty;
    while(!deq.empty())
    {
        var=deq.front();
        if(var.first.x==x&&var.first.y==y&&var.second<strlen(str))
        {
            cout<<"BUG"<<endl;
            return 0;
        }
        if(var.first.x==x&&var.first.y==y&&var.second==strlen(str))
        {
            cout<<"OK"<<endl;
            return 0;
        }
        deq.pop_front();
        tx=var.first.x;
        ty=var.first.y;
        if(tx>0&&robotmap[tx-1][ty]==1)
            deq.push_back(make_pair(xy(tx-1,ty),var.second+1)),robotmap[tx-1][ty]=2;
        if(tx<200&&robotmap[tx+1][ty]==1)
            deq.push_back(make_pair(xy(tx+1,ty),var.second+1)),robotmap[tx+1][ty]=2;
        if(ty>0&&robotmap[tx][ty-1]==1)
            deq.push_back(make_pair(xy(tx,ty-1),var.second+1)),robotmap[tx][ty-1]=2;
        if(ty<200&&robotmap[tx][ty+1]==1)
            deq.push_back(make_pair(xy(tx,ty+1),var.second+1)),robotmap[tx][ty+1]=2;
        
    }

    cout<<"OK"<<endl;
    return 0;
}

#include<iostream>
#include<stdio.h>
#include<string.h>
#include<cmath>
#include<queue>
#include<stack>
#include<set>
#include<algorithm>
#define ll long long
#define oo 1000000007
#define pi acos(-1.0)
#define MAXN 24
using namespace std;  
int girl[2],objects[MAXN][2],dp[1<<MAXN],pre[1<<MAXN];
int arc[MAXN+1][MAXN+1];
int dis(int ax,int ay,int bx,int by)
{
       int x=ax-bx,y=ay-by;
       return x*x+y*y;
}
int main()
{
       int n,i,x,t,p,goal;
       int temp; 
       while (~scanf("%d%d",&girl[0],&girl[1]))
       {
                scanf("%d",&n);
                for (i=0;i<n;i++) scanf("%d%d",&objects[i][0],&objects[i][1]);
                for (i=1;i<=n;i++) arc[i][0]=arc[0][i]=dis(girl[0],girl[1],objects[i-1][0],objects[i-1][1]);
                for (i=1;i<=n;i++)
                   for (x=i;x<=n;x++)
                      arc[i][x]=arc[x][i]=dis(objects[i-1][0],objects[i-1][1],objects[x-1][0],objects[x-1][1]);
                memset(pre,-1,sizeof(pre));
                dp[0]=0;
                goal=(1<<n)-1;
                for (t=1;t<=goal;t++)
                   for (i=0;i<n;i++)
                      if (t & (1<<i))
                      {
                              temp=arc[0][i+1]<<1;
                              p=(t^(1<<i));
                              if (pre[t]==-1 || dp[t]>dp[p]+temp)
                                  dp[t]=dp[p]+temp,pre[t]=p;
                              for (x=i+1;x<n;x++)
                                if (t & (1<<x))
                                { 
                                      temp=arc[0][i+1]+arc[0][x+1]+arc[i+1][x+1]; 
                                      p=t^(1<<i)^(1<<x);
                                      if (pre[t]==-1 || dp[t]>dp[p]+temp)
                                          dp[t]=dp[p]+temp,pre[t]=p;
                                }
                              break; //关键
                      } 
                x=goal;
                printf("%d
",dp[x]);
                while (x)
                {
                      printf("0 ");
                      t=pre[x];
                      for (i=0;i<n;i++)
                         if ((x & (1<<i)) && !(t & (1<<i))) 
                            printf("%d ",i+1);
                      x=t;
                }
                printf("0
");
       }
       return 0;
}
/*
0 0
24
1 1
1 2
1 3
1 4
1 5
1 6
1 7
1 8
1 9
2 0
2 1 
2 2 
2 3 
2 4
2 5
2 6
2 7
2 8
2 9
3 0
3 1
3 2 
3 3 
3 4
*/