100.-same-tree.md

100. Same Tree

{% tabs %} {% tab title="递归" %}

/**
 * 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 isSameTree(TreeNode* p, TreeNode* q) {
        if (!p && !q) return true;
        
        if (!p || !q) return false;
        
        if (p->val != q->val) return false;
        
        return isSameTree(p->left,q->left) && isSameTree(p->right,q->right);
    }
};

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{% tab title="迭代" %}

/**
 * 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 isSameTree(TreeNode* p, TreeNode* q) {
        stack<pair<TreeNode*,TreeNode* >> pairs;
        pairs.push(pair<TreeNode*, TreeNode*>(p, q));
        while (!pairs.empty()) {
            p = pairs.top().first;
            q = pairs.top().second;
            if (!p ^ !q || (p && q && p->val != q->val)){
                break;
            }
            pairs.pop(); // ;;; 终于明白这个梗了
            if (p && q) {
                pairs.push(pair<TreeNode*, TreeNode*> (p->right, q->right));
                pairs.push(pair<TreeNode*, TreeNode*> (p->left, q->left));
            }
        }
        return pairs.empty();
    }
};

{% endtab %} {% endtabs %}