src/main/java/com/fishercoder/solutions/_336.java

package com.fishercoder.solutions;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class _336 {

    public static class Solution1 {
        public List<List<Integer>> palindromePairs(String[] words) {
            List<List<Integer>> pairs = new ArrayList();
            Map<String, Integer> map = new HashMap();
            for (int i = 0; i < words.length; i++) {
                map.put(words[i], i);
            }

            for (int i = 0; i < words.length; i++) {
                int l = 0;
                int r = 0;
                while (l <= r) {
                    String s = words[i].substring(l, r);
                    Integer j = map.get(new StringBuilder(s).reverse().toString());
                    if (j != null && j != i && isPalindrome(
                            words[i].substring(l == 0 ? r : 0, l == 0 ? words[i].length() : l))) {
                        pairs.add(
                                Arrays.asList(l == 0 ? new Integer[]{i, j} : new Integer[]{j, i}));
                    }
                    if (r < words[i].length()) {
                        r++;
                    } else {
                        l++;
                    }
                }
            }
            return pairs;
        }

        private boolean isPalindrome(String s) {
            for (int i = 0; i < s.length() / 2; i++) {
                if (s.charAt(i) != s.charAt(s.length() - 1 - i)) {
                    return false;
                }
            }
            return true;
        }
    }
}