【LeetCode从零单排】No100 Same Tree && No101 Symmetric Tree

题目

1.same tree

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

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

2.symmetric tree

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

For example, this binary tree is symmetric:

    1   / \  2   2 / \ / \3  4 4  3

But the following is not:

    1   / \  2   2   \   \   3    3

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

代码

/** * Definition for binary tree * public class TreeNode { *     int val; *     TreeNode left; *     TreeNode right; *     TreeNode(int x) { val = x; } * } */public class Solution {    public boolean isSameTree(TreeNode p, TreeNode q) {        if(p==null && q==null) return true;        if(p==null || q==null || q.val!=p.val ) return false;        if(isSameTree(p.left,q.left)==false || isSameTree(p.right,q.right)==false) return false;        return true;    }}

/** * Definition for binary tree * public class TreeNode { *     int val; *     TreeNode left; *     TreeNode right; *     TreeNode(int x) { val = x; } * } */public class Solution {    public boolean isSymmetric(TreeNode root) {        if (root==null) return true;        return isEquel(root.left,root.right);    }     public boolean isEquel(TreeNode root1,TreeNode root2){            if(root1==null && root2==null) return true;             if(root1==null || root2==null) return false;            if(root1.val!=root2.val) return false;                        return isEquel(root1.left,root2.right) && isEquel(root2.left,root1.right);                      }}

代码下载：https://github.com/jimenbian/GarvinLeetCode

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