872. Leaf-Similar Trees

题目描述：

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.

解题思路：

DFS方法得到所有的叶子节点，得到叶子节点，判断就很简单了。

代码：

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    bool leafSimilar(TreeNode* root1, TreeNode* root2) {
        vector<int> leafs1;
        vector<int> leafs2;
        getLeaf(root1, leafs1);
        getLeaf(root2, leafs2);
        if (leafs1.size() != leafs2.size())
            return false;
        for (int i = 0; i < leafs1.size(); i++) {
            if (leafs1[i] != leafs2[i])
                return false;
        }
        return true;
    }
    void getLeaf(TreeNode* root, vector<int>& leafs) {
        if (root == NULL)
            return;
        getLeaf(root->left, leafs);
        getLeaf(root->right, leafs);
        if (root->left == NULL && root->right == NULL) {
            leafs.push_back(root->val);
        }
        return;
    }
};