Implement strStr()

Implement strStr().

Returns the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack.

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(H) Shortest Palindrome

1.普通匹配 o(n*m)

class Solution {
public:
int strStr(string haystack, string needle) {
int haystackSize = haystack.size();
int needleSize = needle.size();
if(needleSize ==0){
return 0;
}
int resIndex = 0;
int i=0,j=0,k=0;
while(i<haystackSize && j<needleSize){
if(k>=haystackSize){
break;
}
if(haystack[k]==needle[j]){
k++;
j++;
}else{
i++;
k = i;
j = 0;
}
}
resIndex = j==needleSize ? i:-1;
return resIndex ;
}
};

2.KMP o(n)