Leetcode#144Binary Tree Preorder Traversal

Binary Tree Preorder Traversal

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Question Solution 

Given a binary tree, return the preorder traversal of its nodes‘ values.

For example:
Given binary tree {1,#,2,3},

   1
         2
    /
   3

return [1,2,3].

分析：先序遍历树中的节点，采用递归的方法

public class Solution {

    List<Integer> x=new ArrayList<Integer>();

    void preTra(TreeNode r) {

            if(r!=null)

            {

                x.add(r.val);

                preTra(r.left);

                preTra(r.right);

            }

    }

    public List<Integer> preorderTraversal(TreeNode root) {

            preTra(root);

            return x;

    }

}

Leetcode#144Binary Tree Preorder Traversal

原文：http://7061299.blog.51cto.com/7051299/1653309