UVA 1149 Dominating Patterns

题意：给你一些单词，一个文本字符串，求文本字符串中出现次数最多的单词。

解析：先用word[][]保存单词，然后利用AC自动机来求哪些字符串是匹配的。作为AC自动机入门题目，如果不了解AC自动机的话可以参考http://blog.csdn.net/niushuai666/article/details/7002823，业界良心。AC自动机还有一题入门题，hdu 2222,如果大家有时间的话，可以去看一下。附上我的结题报告链接http://blog.csdn.net/hehedounima/article/details/12184245（貌似这里面关于AC自动机我的注释更详细）

#include"stdio.h"#include"string.h"#include"queue"using namespace std;#define Max 1000010#define maxnode (150*70+10)#define sigma_size 26int num[maxnode],flag[maxnode];char word[151][71];struct AC_automation{struct node{int next[sigma_size];int val;int fail;void init(){memset(next,0,sizeof(next));fail = val = 0;}}ch[maxnode];int sz;int idx(char c){return c - 'a';}void init(){sz = 1;ch[0].init();}void insert(char *s,int x){int u = 0;for(int i = 0 ; s[i] ; i ++){int c = idx(s[i]);if(ch[u].next[c] == 0){ch[sz].init();ch[u].next[c] = sz++;}u = ch[u].next[c];}ch[u].val = 1;flag[u] = x;}void get_fail(){queue<int>Q;for(int i = 0 ; i < sigma_size; i ++)if(ch[0].next[i] != 0)Q.push(ch[0].next[i]);while(!Q.empty()){int temp = Q.front();Q.pop();for(int i = 0 ; i < sigma_size; i ++){if(ch[temp].next[i] != 0){Q.push(ch[temp].next[i]);int fail_temp = ch[temp].fail;while(fail_temp > 0 && ch[fail_temp].next[i] == 0) fail_temp = ch[fail_temp].fail;if(ch[fail_temp].next[i] != 0)fail_temp = ch[fail_temp].next[i];ch[ch[temp].next[i]].fail = fail_temp;  }}}}//求出现次数最多的单词void get_maxnum(char *text){int temp = 0;for(int i = 0 ; text[i] ; i ++){int character = idx(text[i]);while(ch[temp].next[character] == 0){if(temp == 0)  //如果是根节点仍然没有匹配break;temp = ch[temp].fail;}if(ch[temp].next[character]){temp = ch[temp].next[character];if(ch[temp].val)num[temp]++;  //num[i]用来记录i节点单词出现的次数}}}}AC;char text[Max];int N;int main(){while(scanf("%d",&N) != EOF && N != 0){AC.init();memset(flag,0,sizeof(flag));memset(word,0,sizeof(word));memset(num,0,sizeof(num));memset(text,0,sizeof(text));char str_temp[75];for(int i = 0 ; i < N; i ++){scanf("%s",word[i]);AC.insert(word[i],i);}AC.get_fail();scanf("%s",text);AC.get_maxnum(text);int max  = -1;for(int i = 1 ; i < AC.sz; i ++)if(max < num[i])max = num[i];printf("%d\n",max);for(int i = 1 ; i < AC.sz; i ++)if(num[i] == max){printf("%s\n",word[flag[i]]);}}return 0;}