class Solution {
public:
int strStr(string haystack, string needle) {
int hay_len = haystack.length();
int needle_len = needle.length();
int i = 0, j = 0;
int* next = new int[needle_len];
getNext(needle, next);
while(i < hay_len && j < needle_len){
if(j == -1 || haystack[i] == needle[j]){
++i;
++j;
}
else{
j = next[j];
}
}
if(j >= needle_len)
return i - j;
else
return -1;
}
public:
void getNext(string needle, int next[]){
int n = needle.length();
int j = -1;
int i = 0
next[0] = -1;
while(i < n) {
if (j == -1 || needle[i] == needle[j]) {
++i;
++j;
next[i] = j;
}
else
j = next[j];
}
}
};