描述
Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).
Bonus points if you could solve it both recursively and iteratively.
您在真实的面试中是否遇到过这个题?
是
样例
For example, this binary tree {1,2,2,3,4,4,3}
is symmetric:
1
/ \
2 2
/ \ / \
3 4 4 3
But the following {1,2,2,#,3,#,3}
is not:
1
/ \
2 2
\ \
3 3
宽度优先搜索+深度优先搜索:
/** * Definition of TreeNode: * class TreeNode { * public: * int val; * TreeNode *left, *right; * TreeNode(int val) { * this->val = val; * this->left = this->right = NULL; * } * } */ class Solution { public: /** * @param root: root of the given tree * @return: whether it is a mirror of itself */ bool isSymmetric(TreeNode * root) { // Write your code here if(root==NULL) return true; return comparing(root->left,root->right); } bool comparing(TreeNode * left,TreeNode * right){ if(left==NULL&&right==NULL) return true; else if(left==NULL||right==NULL) return false; if(left->val!=right->val) return false; return comparing(left->left,right->right)&&comparing(left->right,right->left); } };