Same Tree
描述
Given two binary trees, write a function to check if they are equal or not.
Two binary trees are considered equal if they are structurally identical and the nodes have the same value.
分析
无
递归版
// Same Tree
// 递归版，时间复杂度O(n)，空间复杂度O(logn)
class Solution {
public:
bool isSameTree(TreeNode *p, TreeNode *q) {
if (!p && !q) return true; // 终止条件
if (!p || !q) return false; // 剪枝
return p->val == q->val // 三方合并
&& isSameTree(p->left, q->left)
&& isSameTree(p->right, q->right);
}
};迭代版
// Same Tree
// 迭代版，时间复杂度O(n)，空间复杂度O(logn)
class Solution {
public:
bool isSameTree(TreeNode *p, TreeNode *q) {
stack<TreeNode*> s;
s.push(p);
s.push(q);
while(!s.empty()) {
p = s.top(); s.pop();
q = s.top(); s.pop();
if (!p && !q) continue;
if (!p || !q) return false;
if (p->val != q->val) return false;
s.push(p->left);
s.push(q->left);
s.push(p->right);
s.push(q->right);
}
return true;
}
};