129. Sum Root to Leaf Numbers

    /*
     * 129. Sum Root to Leaf Numbers 
     * 2016-5-21 By Mingyang
     * dfs包含三种，这里是dfs的preorder方法，先解决根再是左右
     */
    public int sumNumbers(TreeNode root) {
        return dfs(root, 0);
    }
    public int dfs(TreeNode root, int levelBase) {
        if (root == null)
            return 0;
        if (root.left == null && root.right == null) {
            return levelBase + root.val;
        }
        int nextLevelBase = (levelBase + root.val) * 10;
        int leftSubTreeSum = dfs(root.left, nextLevelBase);
        int rightSubTreeSum = dfs(root.right, nextLevelBase);
        return leftSubTreeSum + rightSubTreeSum;
    }
    //自己的代码：
     public int sum=0;
        public int sumNumbers1(TreeNode root) {
            dfs1(root,0);
            return sum;
        }
        public void dfs1(TreeNode root,int base){
            if(root==null)
              return;
            if(root.left==null&&root.right==null){
              sum+=base*10+root.val;
              return;
            }
            base=base*10+root.val;
            if(root.left!=null)
            dfs1(root.left,base);
            if(root.right!=null)
            dfs1(root.right,base);
        }