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symmetric_tree.cpp
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symmetric_tree.cpp
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/*
* =====================================================================================
*
* Filename: symmetric_tree.cpp
*
* Description: 101. Symmetric Tree. Given a binary tree, check whether it is a
* mirror of itself (ie, symmetric around its center).
*
* Version: 1.0
* Created: 02/20/19 11:35:03
* Revision: none
* Compiler: gcc
*
* Author: Zhu Xianfeng (), [email protected]
* Organization:
*
* =====================================================================================
*/
#include <stdio.h>
#include <queue>
struct TreeNode
{
int val;
TreeNode* left;
TreeNode* right;
TreeNode(int x) : val(x), left(NULL), right(NULL) {}
};
// Recursive
class Solution1
{
public:
bool isSymmetric(TreeNode* root)
{
if (root == NULL)
{
return true;
}
return isSymmetric(root->left, root->right);
}
private:
bool isSymmetric(TreeNode* a, TreeNode* b)
{
if (a == NULL && b == NULL)
{
return true;
}
else if (a == NULL || b == NULL)
{
return false;
}
else if (a->val != b->val)
{
return false;
}
return (isSymmetric(a->left, b->right) && isSymmetric(a->right, b->left));
}
};
// Iterative
class Solution2
{
public:
bool isSymmetric(TreeNode* root)
{
if (root == NULL)
{
return true;
}
std::queue<TreeNode*> nodes;
nodes.push(root->left);
nodes.push(root->right);
while (!nodes.empty())
{
auto* a = nodes.front();
nodes.pop();
auto* b = nodes.front();
nodes.pop();
if (a == NULL && b == NULL)
{
continue;
}
else if (a == NULL || b == NULL || a->val != b->val)
{
return false;
}
// Push subnodes
nodes.push(a->left);
nodes.push(b->right);
nodes.push(a->right);
nodes.push(b->left);
}
return true;
}
};
using Solution = Solution2;
int main(int argc, char* argv[])
{
TreeNode* root = NULL;
auto is_symmetric = Solution().isSymmetric(root);
printf("Is symmetric? %s\n", is_symmetric ? "true" : "false");
return 0;
}