KMP演算法，字串匹配

/*<br />過了一年再學KMP，為AC自動機做準備。<br />嚴蔚敏的《資料結構》P82講的還算清楚。<br />不想學的直接拉去做模板吧，適合一個字串去匹配多個目標串。<br />*/<br />#include <stdio.h><br />#include <string.h><br />const int MaxN = 1000;<br />char a[MaxN] , b[MaxN];<br />int next[MaxN];<br />void get_next(char *s)<br />{<br />next[1] = 0;<br />int i = 1 , j = 0 , l = strlen(s --);<br />while (i < l){<br />if (j == 0 || s[i] == s[j]){<br />i ++;<br />j ++;<br />next[i] = s[i] != s[j] ? j : next[j];<br />}else{<br />j = next[j];<br />}<br />}<br />}<br />int kmp(char *a , char *b)<br />{<br />int n = strlen(a --) , m = strlen(b --);<br />int i = 0 , j = 0;<br />while (i <= n && j <= m){<br />if (j == 0 || a[i] == b[j]){<br />i ++;<br />j ++;<br />}else{<br />j = next[j];<br />}<br />}<br />return j > m ? i - m - 1 : -1;<br />}</p><p>void __test()<br />{<br />scanf("%s%s" , a , b);<br />get_next(b);<br />printf("%d/n" , kmp(a , b));<br />}<br />int main()<br />{<br />__test();<br />}