POJ 1204 Word Puzzles（AC自动机）

每次找到了一个串的头，就要回去找他的前驱结点因为有可能模式串为abcd bcd如果不找前驱结点bcd的开始位置永远找不到。

////  main.cpp//  Richard////  Created by 邵金杰 on 16/9/2.//  Copyright © 2016年 邵金杰. All rights reserved.//#include<iostream>#include<cstdio>#include<string>#include<algorithm>#include<queue>#include<vector>#include<cstring>using namespace std;const int maxn=1000000+100;const int N=1000+10;string map[N];struct node{    node *child[26];    node *pre;    int pos;    bool badnode;    void intial(){        memset(child,0,sizeof(child));        pos=0;        badnode=false;        pre=NULL;    }}tree[maxn];int ncount;pair<int,int> pa[N];char dire[N];string s;int r,c,w;const int dx[]={-1,-1,0,1,1, 1, 0,-1};const int dy[]={ 0, 1,1,1,0,-1,-1,-1};const char dir[]={"EFGHABCD"};void Insert(node *p,int no){    for(int i=0;s[i];i++)    {        if(p->child[s[i]-'A']==NULL)        {            p->child[s[i]-'A']=tree+ncount;            ncount++;        }        p=p->child[s[i]-'A'];    }    p->badnode=true;    p->pos=no;}void BuildDFA(){    for(int i=0;i<26;i++)        tree[0].child[i]=tree+1;    tree[0].pre=NULL;    tree[1].pre=tree;    queue<node*> q;    q.push(tree+1);    while(!q.empty())    {        node *proot=q.front();        q.pop();        for(int i=0;i<26;i++)        {            node *p=proot->child[i];            if(p)            {                node *pre=proot->pre;                while(pre)                {                    if(pre->child[i]!=NULL)                    {                        p->pre=pre->child[i];                        break;                    }                    else                        pre=pre->pre;                }                q.push(p);            }        }    }}bool inside(int x,int y){    return x>=0&&x<r&&y>=0&&y<c;}void searchDFA(int i,int j,int k){    node *p=tree+1;    int x=i,y=j;    while(true)    {        if(!inside(x,y)) break;        while(true)        {            if(p->child[map[x][y]-'A']!=NULL){                p=p->child[map[x][y]-'A'];                node *pre=p;                while(pre->badnode) {                    if(pre->pos){                    pa[pre->pos].first=x;                    pa[pre->pos].second=y;                    dire[pre->pos]=dir[k];                    pre->pos=0;                    }                    pre=pre->pre;                }                break;            }            else p=p->pre;        }        x+=dx[k];        y+=dy[k];    }}void work(){    for(int i=0;i<r;i++)    {        searchDFA(i,0,2);        searchDFA(i,c-1,6);        searchDFA(i,0,1);        searchDFA(i,0,3);        searchDFA(i,c-1,7);        searchDFA(i,c-1,5);    }    for(int j=0;j<c;j++)    {        searchDFA(0,j,4);        searchDFA(r-1,j,0);        searchDFA(0,j,5);        searchDFA(0,j,3);        searchDFA(r-1,j,1);        searchDFA(r-1,j,7);    }    for(int i=1;i<=w;i++)    {        cout<<pa[i].first<<' '<<pa[i].second<<' '<<dire[i]<<endl;    }}int main(){    cin>>r>>c>>w;    ncount=2;    for(int i=0;i<r;i++)        cin>>map[i];    for(int i=1;i<=w;i++)    {        cin>>s;        reverse(s.begin(),s.end());        Insert(tree+1,i);    }    BuildDFA();    work();    return 0;}