LeetCode 0100 0101

100. Same Tree

Easy

Given two binary trees, write a function to check if they are the same or not.

Two binary trees are considered the same if they are structurally identical and the nodes have the same value.

Example 1:

Input: 1         1
          / \       / \
         2   3     2   3

        [1,2,3],   [1,2,3] Output: true

Example 2:

Input: 1         1
          /           \
         2             2

        [1,2],     [1,null,2] Output: false

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 * int val;
 * struct TreeNode *left;
 * struct TreeNode *right;
 * };
 */
bool isSameTree(struct TreeNode* p, struct TreeNode* q) {
    if(p==NULL && q==NULL)
        return 1;
    if(p!=NULL && q!=NULL && p->val==q->val){
        return isSameTree(p->left,q->left)&&isSameTree(p->right,q->right);
    }
    return 0;
}

101. Symmetric Tree

Easy

Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).

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,null,3,null,3] is not:

    1
   / \
  2   2
   \   \
   3    3

Note:
Bonus points if you could solve it both recursively and iteratively.

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 * int val;
 * struct TreeNode *left;
 * struct TreeNode *right;
 * };
 */
bool is_mirror(struct TreeNode *p, struct TreeNode* q){
    if(p==NULL && q==NULL)
        return 1;
    if(p!=NULL && q!=NULL && p->val==q->val)
        return is_mirror(p->left,q->right) && is_mirror(p->right,q->left);
    return 0;
}
bool isSymmetric(struct TreeNode* root) {
    if(root==NULL)
        return 1;
    return is_mirror(root->left,root->right);
}