131.palindrome-partitioning.java

/*
 * @lc app=leetcode id=131 lang=java
 *
 * [131] Palindrome Partitioning
 *
 * https://leetcode.com/problems/palindrome-partitioning/description/
 *
 * algorithms
 * Medium (45.42%)
 * Likes:    1574
 * Dislikes: 58
 * Total Accepted:    212.8K
 * Total Submissions: 466K
 * Testcase Example:  '"aab"'
 *
 * Given a string s, partition s such that every substring of the partition is
 * a palindrome.
 * 
 * Return all possible palindrome partitioning of s.
 * 
 * Example:
 * 
 * 
 * Input: "aab"
 * Output:
 * [
 * ⁠ ["aa","b"],
 * ⁠ ["a","a","b"]
 * ]
 * 
 * 
 */

// @lc code=start
class Solution {
    public List<List<String>> partition(String s) {
        List<List<String>> result = new ArrayList<>();
        dfs(s, 0, new ArrayList<String>(), result);
        return result;
    }
    
    private void dfs(String s, int start, List<String> path, List<List<String>> result) {
        if (start >= s.length()) {
            result.add(new ArrayList<>(path));
            return;
        }
        
        for (int i = start; i < s.length(); i++) {
            String curr = s.substring(start, i+1);
            if (isPalindrome(curr)) {
                path.add(curr);
                dfs(s, i + 1, path, result);
                path.remove(path.size() - 1);
            }
        }
    }
    
    private boolean isPalindrome(String s) {
        if (s.length() <= 1) return true;
        int l = 0, r = s.length() - 1;
        while (l < r) {
            if (s.charAt(l) != s.charAt(r)) return false;
            l++;
            r--;
        }
        return true;
    }
}
// @lc code=end