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SymmetricTree.cpp
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63 lines (55 loc) · 1.56 KB
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/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
// 循环解法
class Solution {
public:
bool isSymmetric(TreeNode* root) {
if (root == NULL)
return true;
queue<TreeNode*> qTree;
qTree.push(root->left);
qTree.push(root->right);
while (!qTree.empty())
{
TreeNode* ltr = qTree.front();
qTree.pop();
TreeNode* rtr = qTree.front();
qTree.pop();
if (ltr == NULL && rtr == NULL)
continue;
if ((ltr != NULL && rtr == NULL) || (ltr == NULL && rtr != NULL)
|| (ltr->val != rtr->val))
return false;
qTree.push(ltr->left);
qTree.push(rtr->right);
qTree.push(ltr->right);
qTree.push(rtr->left);
}
return true;
}
};
// 递归解法
class Solution {
public:
bool isSymmetric(TreeNode* root) {
if (root == NULL)
return true;
return helper(root->left, root->right);
}
bool helper(TreeNode* leftSub, TreeNode* rightSub)
{
if (leftSub == NULL && rightSub == NULL)
return true;
if ((leftSub == NULL && rightSub != NULL) || (leftSub != NULL && rightSub == NULL)
|| (leftSub->val != rightSub->val))
return false;
return helper(leftSub->left, rightSub->right) && helper(leftSub->right, rightSub->left);
}
};