Java学习之二叉树

最近在刷leetcode，虽然还是很菜，但是我决定这学期刷完easy和medium！然后寒假继续刷然后就投简历找暑假实习啦。

而且这两天学的linux是关于线程管理，系统启动流程的。感觉还没有理解透，所以就没有写博客。我一定会补上的！！ORZ

递归一直是短板，所以就决定写几篇博客分析递归，方便以后复习。

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题目：

Consider all the leaves of a binary tree.  From left to right order, the values of those leaves form a leaf value sequence.

For example, in the given tree above, the leaf value sequence is (6, 7, 4, 9, 8).

Two binary trees are considered leaf-similar if their leaf value sequence is the same.

Return true if and only if the two given trees with head nodes root1 and root2 are leaf-similar.

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public boolean leafSimilar(TreeNode root1, TreeNode root2) {
        if(root1==null&&root2==null)
            return true;
        if(root1==null||root2==null)
            return false;
        StringBuilder leaf_t1=new StringBuilder();
        StringBuilder leaf_t2=new StringBuilder();
        getLeaves(leaf_t1,root1);
        getLeaves(leaf_t2,root2);
        return leaf_t1.toString().equals(leaf_t2.toString());
    }
    
    private void getLeaves(StringBuilder sb,TreeNode root){
        if(root==null)
            return;
        getLeaves(sb,root.left);
        if(root.left==null && root.right==null){
            sb.append(root.val);
        }
        getLeaves(sb,root.right);
        return;
    }
}