Leaf-Similar Trees

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.

 

Constraints:

Both of the given trees will have between 1 and 200 nodes.
Both of the given trees will have values between 0 and 200

这题很简单，检查两个树的叶子节点的值是否一致。直接用先序遍历就可以得到所有叶子节点的值。

struct TreeNode {
    int val;
    TreeNode *left;
    TreeNode *right;
    TreeNode() : val(0), left(nullptr), right(nullptr) {}
    TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
    TreeNode(int x, TreeNode *left, TreeNode *right)
        : val(x), left(left), right(right) {}
};

class Solution {
public:
    bool leafSimilar(TreeNode* root1, TreeNode* root2) {
        vector<int> lv;
        vector<int> rv;
        lvs(root1, lv);
        lvs(root2, rv);
        return lv == rv;   
    }

    void lvs(TreeNode *root, vector<int> &res) {
        if (root->left == nullptr && root->right == nullptr) {
            res.push_back(root->val);
            return;
        }
        if (nullptr != root->left) {
            lvs(root->left, res);
        }
        if (nullptr != root->right) {
            lvs(root->right, res);
        }
    }
};