336 Palindrome Pairs

Given a list of unique words, find all pairs of distinct indices (i, j) in the given list, so that the concatenation of the two words, i.e. words[i] + words[j] is a palindrome.

Example 1:

Input: ["abcd","dcba","lls","s","sssll"]
Output: [[0,1],[1,0],[3,2],[2,4]] 
Explanation: The palindromes are ["dcbaabcd","abcddcba","slls","llssssll"]


 public List<List<Integer>> palindromePairs(String[] words) {
        List<List<Integer>> result = new ArrayList();
        int n = words.length;
        
        for(int i=0;i<n;i++){
            for(int j=i+1;j<n;j++){
                
                if(isPalindrome(words[i]+words[j])){ 
                    result.add(Arrays.asList(i,j));
                }
                
                if(isPalindrome(words[j]+words[i])){ 
                     result.add(Arrays.asList(j,i));
                }
            }
        }
        
        return result;     
    }
    
    static boolean isPalindrome(String temp){
        int i = 0;
        int j = temp.length()-1;
        while(i<j){
            if(temp.charAt(i)!=temp.charAt(j)) return false; 
            i++;j--;
        }
        return true;
    }