字符串匹配算法SMA 总结之四：自动机算法

自动机匹配算法常使用链表表示，这里使用数组，占用的空间太大了些，

有时间详细说说

#include <iostream>using namespace std;const int alphabet_len=128;//construct an automation/*int*/void preAuto(int* automation,const char* pattern,const int pattern_len){//int state=0;for (int i=0;i<pattern_len;i++){int reserve=automation[i*alphabet_len+pattern[i]];automation[i*alphabet_len+pattern[i]]=i+1;memcpy(automation+(i+1)*alphabet_len,automation+reserve*alphabet_len,alphabet_len*sizeof(int));}}int dfa(const char* text,const int text_len,const char* pattern,const int pattern_len){//allocate memory for automationint* automation=new int[(pattern_len+1)*alphabet_len];//initializationfor (int i=0;i<(pattern_len+1)*alphabet_len;i++){automation[i]=0;}//preprocessingpreAuto(automation,pattern,pattern_len);int result=-1;//searchingint auto_state=0;for (int i=0;i<text_len;i++){auto_state=automation[auto_state*alphabet_len+text[i]];if (auto_state==pattern_len){result= i-pattern_len+1;break;}}delete[] automation;return result;}