包含匹配算法和获取next数组的方法
class Solution {
public int strStr(String haystack, String needle) {
if(needle.isEmpty()) return 0;
int i=-1,j=-1;
int m=haystack.length();
int n=needle.length();
int[] next=getNext(needle);
while(i<m&&j<n){
if(j==-1||(haystack.charAt(i)==needle.charAt(j))){
i++;
j++;
}else{
j=next[j];
}
}
if(j>n-1){
return i-j;
}
return -1;
}
private int[] getNext(String str){
int[] next=new int[str.length()];
int i=0,j=-1;
next[0]=-1;
while(i<str.length()-1){
if(j==-1||str.charAt(i)==str.charAt(j)){
i++;
j++;
next[i]=j;
}else{
j=next[j];
}
}
return next;
}
}