LeetCode28:

 . - 力扣（LeetCode）

public class KMP {public static void main(String[] args) {KMP kmp=new KMP();kmp.strStr("aabaabaaf","aabaaf");}public int strStr(String haystack, String needle) {//获取next数组int[] next=getNext(needle);//根据next数组，进行匹配int i=0;for (int j = 0; j < haystack.length()&&j+needle.length()<haystack.length(); j++) {while (i>0&&haystack.charAt(j)!=needle.charAt(i)){i=next[i-1];}if (haystack.charAt(j)==needle.charAt(i)){i++;}if (i==needle.length()){return j-i+1;}}return -1;}private int[] getNext(String needle) {int[] next=new int[needle.length()];next[0]=0;int j=0; //前缀的末尾，也是最长相等前后缀的长度int i;//后缀的末尾for (i = 1; i <needle.length(); i++) {while (j>0&&needle.charAt(i)!=needle.charAt(j)){j=next[j-1];}if (needle.charAt(i)==needle.charAt(j)){j++;next[i]=j;}}return next;}}

LeetCode459:
. - 力扣（LeetCode）

public class LeetCode459 {public boolean repeatedSubstringPattern(String s) {//查找子串，就是查找s.length-最长前后缀的长度对应的子串int[] next = getNext(s);if (next[s.length()-1]!=0&&(s.length()%(s.length()-next[s.length()-1])==0)){return true;}return false;}private int[] getNext(String model){int[] next=new int[model.length()];next[0]=0;int j=0; //前缀的尾部，也是最长前后缀的长度int i;//后缀的尾部for (i = 1; i <model.length(); i++) {while (j>0&&model.charAt(j)!=model.charAt(i)){j=next[j-1];}if (model.charAt(j)==model.charAt(i)){j++;}next[i]=j;}return next;}
}