Same Tree(100)

Same Tree

Given two binary trees, write a function to check if they are equal or

1. Two binary trees are considered equal if they are structurally

2. and the nodes have the same value.

思路： recursion, 注意判断条件不应该 if(p.val == q.val) return true,因为这样后面没有比较就比较了当前层, 要确保比较到最底层 if (p == null && q == null) 再返回true;

时间复杂度： O(n) n为节点数
空间复杂度： O(h) h为树的高度

public class Solution {
public boolean isSameTree(TreeNode p, TreeNode q) {
if (p == null && q == null) {
return true;
}
if (p == null || q == null) {
return false;
}
if (p.val != q.val) {
return false;
}
return isSameTree(p.left, q.left) && isSameTree(p.right, q.right);
}
}

关键字：tree, recursion, null, return