Shortest Palindrome

 1 public class Solution {
 2     public String shortestPalindrome(String s) {
 3         if (s.length() < 2) {
 4             return s;
 5         }
 6         String newS = s + "#" + new StringBuilder(s).reverse().toString();
 7         int[] pos = new int[newS.length()];
 8         
 9         for (int i = 1; i < newS.length(); i++) {
10             int prePos = pos[i - 1];
11             while (prePos > 0 && newS.charAt(prePos) != newS.charAt(i)) {
12                 prePos = pos[prePos - 1];
13             }
14             pos[i] = prePos + ((newS.charAt(i) == newS.charAt(prePos)) ? 1 : 0);
15         }
16         return new StringBuilder(s.substring(pos[pos.length - 1])).reverse().toString() + s;
17     }
18 }

KMP

posted on 2016-07-08 12:49 keepshuatishuati 阅读(131) 评论(0) 编辑收藏举报