"Leetcode-Interview algorithm classic-java implementation" "101-symmetric Tree (symmetric tree)"

"101-symmetric tree (symmetric trees)" "leetcode-Interview algorithm classic-java Implementation" "All topics Directory Index" Original Question

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

    1     2   \ 3  4 4  3

But the following are not:

    1     2   2   \      3    3

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

Main Topic

Given a tree, judge whether it is symmetrical. That is, whether the tree's Zuozi is a mirror image of its right subtree.

Thinking of solving problems

Using recursion to solve, first determine whether the left and right sub-nodes are equal, not equal to return false, equality will be left dial hand node Zuozi and right child results of the right sub-node to compare operations, at the same time the left Dial hand node of the Zuozi and the left sub-node is compared, only two at the same time true, Otherwise, false is returned.

Code Implementation

Tree Node class

publicclass TreeNode {    int val;    TreeNode left;    TreeNode right;    TreeNode(int x) { val = x; }}

Algorithm implementation class

 Public classSolution { PublicBoolean issymmetric (TreeNode root) {if(Root = =NULL) {returntrue; }Else{return issame (root). Left, Root. Right); }    }PrivateBoolean Issame (TreeNode Left, TreeNode Right) {if( Left==NULL&& Right==NULL) {returntrue; }if( Left!=NULL&& Right==NULL|| Left==NULL&& Right!=NULL) {returnfalse; }Else{return Left. val = = Right. Val && Issame ( Left. Left, Right. Right) && Issame ( Left. Right, Right. Left); }    }}

Evaluation Results

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"Leetcode-Interview algorithm classic-java implementation" "101-symmetric Tree (symmetric tree)"