int strStr(char *haystack, char *needle) {
if(needle[0] == '\0')
return 0;
int m = strlen(haystack);
int n = strlen(needle);
vector<int> nxt(n + 1);
calNext(needle, n, nxt);
int i = 0;
int j = 0;
while(i < m)
{
if(j == -1 || haystack[i] == needle[j])
{
++i;
++j;
}
else
{
j = nxt[j];
}
if(j == n)
return i - j;
}
return -1;
}
string shortestPalindrome(string s) {
if (s.size() <= 1)
return s;
string t = s;
reverse(t.begin(), t.end());
s = s+"#"+t;
vector<int> next;
calNext(next, s);
s = t;
reverse(s.begin(), s.end());
return t.substr(0, t.size()-next.back()) + s;
}
