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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.
Note:
Both of the given trees will have between 1 and 100 nodes.
讲解
这道题的思路很简单，先扫描出两个树的叶子结果集，然后比较就行了。考察点是树的遍历。递归的时候首先要判断结点是否为空。
Java 代码
/**
* 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) {
List<Integer> leaves1 = new ArrayList<>();
List<Integer> leaves2 = new ArrayList<>();
getLeaves(root1, leaves1);
getLeaves(root2, leaves2);
if(leaves1.size()!=leaves2.size()){
return false;
}else{
for(int i=0;i<leaves1.size();i++){
if(leaves1.get(i)!=leaves2.get(i)){
return false;
}
}
}
return true;
}
private void getLeaves(TreeNode root, List<Integer> leaves){
if(root==null){
return;
}
if(root.left==null && root.right==null){
leaves.add(root.val);
return;
}
getLeaves(root.left, leaves);
getLeaves(root.right, leaves);
}
}
