LeetCode-Leaf-Similar Trees

最新推荐文章于 2019-05-05 20:05:28 发布

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本文介绍了一种判断两棵二叉树叶子节点序列是否相同的方法。通过遍历二叉树并收集叶子节点值形成序列，最终比较两序列是否一致来实现。适用于1到100个节点的二叉树。

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Description：
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.

Note:
Both of the given trees will have between 1 and 100 nodes.

题意：给定两棵树，每棵树的叶子序列为从左至右的顺序，判断两棵树的叶子序列是否相同(序列相同要求每一位上的数字都相同，而不是排序后每一位上的数字相同)；

解法：既然要求比较叶子序列，我们可以对二叉树进行遍历，将叶子节点值存储在字符串中，最后比较叶子节点的两个字符串内容是否相同就可以了；

/**
 * 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){
            return root2 == null ? true : false;
        }
        String leaves1 = getLeaves(root1, "");
        String leaves2 = getLeaves(root2, "");
        return leaves1.equals(leaves2) ? true : false;
    }

    private String getLeaves(TreeNode root, String leaves){
        if(root.left == null && root.right == null){
            return "" + root.val;
        }//添加叶子节点
        if(root.left  != null) leaves += getLeaves(root.left,  "");
        if(root.right != null) leaves += getLeaves(root.right, "");
        return leaves;
    }
}