Why my solution is so slow? It's a common recursion version.


  • 0
    P

    My code was accepted, but the running time is somehow long. I have compared my code with the sample code and I can't figure out why.


    public class Solution {
    public List<List<Integer>> pathSum(TreeNode root, int target) {
    return biTreePathSumHelper(root, target, new ArrayList<Integer>(),
    new ArrayList<List<Integer>>(), 0);
    }

    private List<List<Integer>> biTreePathSumHelper(TreeNode root, 
                                                   int target, 
                                                   List<Integer> path,
                                                   List<List<Integer>> 
                                                   paths, int sum) {
        if (root == null) {
            return paths;
        } 
        sum += root.val;
        path = new ArrayList<Integer>(path);
        path.add(root.val);
        if (root.left == null && root.right == null) {
            if (sum == target) {
                paths.add(path);
            }
            return paths;
        }
        paths = biTreePathSumHelper(root.left, target, path, paths, sum);
        paths = biTreePathSumHelper(root.right, target, path, paths, sum);
        return paths;
    }
    

    }



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