【Leetcode】100. Same Tree-优快云博客

本文提供两种方法来检查两棵二叉树是否等价，即它们是否在结构上相同且节点值相等。一种是非递归方法，使用了两个链表来存储树的节点并进行比较；另一种是递归方法，直接通过递归调用来实现节点的对比。

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Question：

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.

My Solution （no recursion）：1ms

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    LinkedList<TreeNode> plist = new LinkedList<TreeNode>();
    LinkedList<TreeNode> qlist = new LinkedList<TreeNode>();
    public boolean isSameTree(TreeNode p, TreeNode q) {
        plist.push(p);
        qlist.push(q);
        while(plist.size() > 0 && qlist.size() > 0){
            TreeNode p1 = plist.pop();
            TreeNode q1 = qlist.pop();
            if(!compare(p1,q1)){
                return false;
            }
        }
        if(plist.size() == qlist.size()){
            return true;
        }else{
            return false;
        }

    }
    public boolean compare(TreeNode p, TreeNode q){
        if(p == null && q == null){
            return true;
        }else if(p != null && q != null){
            if(p.val == q.val){
                if(compareChild(p.left,q.left)){
                    if(compareChild(p.right,q.right)){
                        return true;                        
                    }
                }
            }
        }

        return false;
    }
    public boolean compareChild(TreeNode p, TreeNode q){
        if(p == null && q == null){
            return true;
        }else if(p != null && q != null){
            if(p.val == q.val){
                plist.offer(p);
                qlist.offer(q);
                return true;
            }   
        }
        return false;
    }
}

My solution 2 (recursion): 0ms

/**
 * Definition for a binary tree node.
 * 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(!compare(p,q)){
            return false;
        }
        return true;
    }
    public boolean compare(TreeNode p, TreeNode q){
        if(p == null && q == null){
            return true;
        }else if(p != null && q != null){
            if(p.val == q.val){
                if(compare(p.left,q.left)){
                    if(compare(p.right,q.right)){
                        return true;                        
                    }
                }
            }
        }

        return false;
    }

}