Leaf-Similar Trees

Leaf-Similar Trees - LeetCode

Thinkings

二叉树无论先中后序遍历，所得叶子节点次序不变.

Codes

我采用了非递归的中序遍历方式：

/**
 * Definition for a binary tree node.
 * 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) {
        std::vector<int> leaf1;
        std::vector<int> leaf2;

        // InOrder Traverse
        std::stack<TreeNode*> stack1;
        TreeNode* p1 = root1;
        while (p1 || !stack1.empty()) {
            if (p1) {
                stack1.push(p1);
                p1 = p1->left;
            } else {
                p1 = stack1.top();
                stack1.pop();
                if (!p1->right) {
                    leaf1.push_back(p1->val);
                }
                p1 = p1->right;
            }
        }

        std::stack<TreeNode*> stack2;
        TreeNode* p2 = root2;
        while (p2 || !stack2.empty()) {
            if (p2) {
                stack2.push(p2);
                p2 = p2->left;
            } else {
                p2 = stack2.top();
                stack2.pop();
                if (!p2->right) {
                    leaf2.push_back(p2->val);
                }
                p2 = p2->right;
            }
        }

        return leaf1 == leaf2;
    }
};