-
Notifications
You must be signed in to change notification settings - Fork 0
Expand file tree
/
Copy pathLongestEchoString.java
More file actions
54 lines (52 loc) · 1.67 KB
/
LongestEchoString.java
File metadata and controls
54 lines (52 loc) · 1.67 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
import java.util.Scanner;
public class LongestEchoString {
/* public static void main(String[] args){
Scanner sc = new Scanner(System.in);
String s = sc.next();
String result = longestPalindrome(s);
System.out.println(result);
}
public static String longestPalindrome(String s) {
int n = s.length();
String result = "";
boolean[][] booleans = new boolean[n][n];
for(int i = 0; i < n ; i++) {
for(int j = i; j >= 0 ; j--) {
if(s.charAt(i) == s.charAt(j) && ((i-j < 2) || booleans[i-1][j+1] )){
booleans[i][j] = true;
}
if(booleans[i][j] && ((i-j+1) > result.length()) ){
result = s.substring(j, i+1);
}
}
}
return result;
}
*/
public static void main(String[] args) {
System.out.println(longestPalindrome("abbad"));
}
public static String longestPalindrome(String s) {
int n = s.length();
if(n == 0) return "";
int start = 0;
int end = 0;
for(int i = 0; i < n; i++) {
int len1 = helper(s, i, i);
int len2 = helper(s, i, i + 1);
int len = Math.max(len1, len2);
if(len > end - start) {
start = i - (len - 1) / 2;
end = i + len / 2;
}
}
return s.substring(start, end + 1);
}
public static int helper(String s, int left, int right) {
while(left >= 0 && right < s.length() && s.charAt(left) == s.charAt(right)) {
left--;
right++;
}
return right - left - 1;
}
}