void knuth_morris_pratt(string s, string t, vector<int>& pos)
{//字符串s在文本t中进行匹配
//返回字符串在文本中匹配到的子串的数量和位置，存储于数组pos中
pos.clear();
int pref[MAX];
//计算字符串s的前缀函数pref
compute_prefix(s, pref);
int i(0);
while(i < (int)t.length()){
int q(0);
while(q < (int)s.length() && s[q] == t[i + q])
++ q;
if(q == (int)s.length())
pos.push_back(i);
if(q == 0)
++ i;
else
//移动位移i = q - prefix[q - 1]
//这里的q是字符串不匹配的字符下标
i += q - pref[q - 1];
}
}
/*KMP：成功返回第一次匹配位置，失败返回-1*/
int kmp(const char *text, const char *pattern)
{
int i;
int j = -1;
const int n = strlen(text);
const int m = strlen(pattern);
if (n == 0 && m == 0)return 0;
if (m == 0)return 0;
int *next = (int*)malloc(sizeof(int)*m);
compute_prefix(pattern, next);
for (i = 0; i < n; i++){
while (j>-1 && pattern[j + 1] != text[i])
j = next[j];
if (text[i] == pattern[j + 1])j++;
if (j == m - 1){
free(next);
return i - j;
}
}
free(next);
return -1;
}
