LeetCode第[5]题(Java)：LongestPalindromicSubstring标签：String、动态规划

Input: "babad"

Output: "bab"

Note: "aba" is also a valid answer.

 1     public String longestPalindrome(String s) {
 2         int n = s.length();
 3         String ans = "";
 4         Set set = new HashSet();
 5         for (int i = 0; i ) {
 6             for (int j = i + 1; j <= n; j++) {
 7                 set.add(s.substring(i, j));
 8             }
 9         }
10         for (String m : set) {
11             if (isPalindromic(m)) {
12                 ans = m.length()>ans.length()?m:ans;
13             }
14         }
15         return ans;
16     }
17     
18     public boolean isPalindromic (String m) {
19         String reverse = new StringBuffer(m).reverse().toString();
20         return m.equals(reverse) ? true : false;
21     }

 1 class Solution {
 2     String ans = "";
 3     public String longestPalindrome(String s) {
 4         for (int i = 0;i ) {
 5             extendVerify(s,i,i);
 6             extendVerify(s,i,i+1);
 7         }
 8         return ans;
 9     }
10     public void extendVerify(String s, int j, int k) {
11         while (j >= 0 && k  s.charAt(k)) {
12             j--;
13             k++;
14         }
15         String subString = s.substring(j+1,k);
16         ans = subString.length()>ans.length()?subString:ans;
17     }
18 }