257. Binary Tree Paths

[Shawngbk]

DFS

SOL1: public class Solution { public List binaryTreePaths(TreeNode root) { List res = new ArrayList<>(); if(root != null) SearchDFS(root, "", res); return res; }

private void SearchDFS(TreeNode root, String path, List<String> res) {
    if(root.left == null && root.right == null)
    res.add(path + root.val);
    if(root.left != null)
    SearchDFS(root.left, path + root.val + "->", res);
    if(root.right != null)
    SearchDFS(root.right, path + root.val + "->", res);
}

}

Sol.2 public List binaryTreePaths(TreeNode root) { List res = new ArrayList<>(); if(root == null) return res; String path = new String(); TreeNode p = root; Stack stack = new Stack<>(); Stack pathStack = new Stack<>(); TreeNode pre = null; while(p!=null || !stack.isEmpty()) { if(p!=null) { if(p == root) path = Integer.toString(p.val); else path = path+"->"+Integer.toString(p.val);

        if(p.left == null && p.right == null)
            res.add(path);
        pathStack.push(path);
        stack.push(p);
        pre = p;
        p = p.left;
    }
    else
    {
        TreeNode node = stack.pop();
        p = node.right;
        path = pathStack.pop();
    }
}
return res;

}

[Shawngbk]

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