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LongestPalindrome.java
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144 lines (83 loc) · 2.15 KB
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package com.vinay.practice.lc;
import java.util.HashMap;
import java.util.Map;
public class LongestPalindrome {
public static void main(String[] args) {
// TODO Auto-generated method stub
System.out.println(longestPalindrome("avscvfdbbbba"));
}
public static String longestPalindrome(String s) {
int start = 0;
int end = 1;
int n =s.length();
int low, high;
for(int i=0; i<n; i++) {
// tackle even palin substring bbaabb avscvfdbbbba
low = i-1;
high = i;
while(low >= 0 && high < n && s.charAt(low) == s.charAt(high)) {
if(high-low+1 > end) {
start = low;
end = high-low+1;
}
low--;
high++;
}
// tackle odd palin string racecar
low = i-1;
high = i+1;
while(low >= 0 && high < n && s.charAt(low) == s.charAt(high)) {
if(high-low+1 > end) {
start = low;
end = high-low+1;
}
low--;
high++;
}
}
return getSubstring(s, start, start+end-1);
}
public static String getSubstring(String s, int start, int end) {
StringBuilder sb = new StringBuilder();
while(start <= end) {
sb.append(s.charAt(start));
start++;
}
return sb.toString();
}
public static void longestPalindromeTle(String s) {
Map<String, Integer> map = new HashMap<String, Integer>();
Integer length;
for(int i=0; i<s.length(); i++) {
for(int j=i+1; j<=s.length(); j++) {
String sub = s.substring(i,j);
if(isPalindrome(sub)) {
length = sub.length();
map.put(sub, length);
}
}
}
String keyFinal = null;
Integer tempVal = Integer.MIN_VALUE;
System.out.println(map.entrySet().toString());
for (Map.Entry<String, Integer> entry : map.entrySet()) {
String key = entry.getKey();
Integer val = entry.getValue();
if(tempVal < val) {
tempVal = val;
keyFinal = key;
}
}
System.out.println(keyFinal);
}
public static boolean isPalindrome(String s) {
for(int i=0,j=s.length()-1; i<j; i++,j--) {
if(s.charAt(i) == s.charAt(j)) {
continue;
} else {
return false;
}
}
return true;
}
}