[leetcode]100. Same Tree相同的树

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

 

 

 

题意：

给定两个树，判断两个数是否相同

 

Solution1：  DFS  (Code will be neat and simple)

 

 

code

class Solution {
    public boolean isSameTree(TreeNode p, TreeNode q) {
        if(p ==null && q ==null) return true;
        if(p ==null || q ==null) return false;  
        
        if(p.val == q.val){
             return  isSameTree(p.left, q.left) && isSameTree(p.right, q.right);
        }
        return false;   
    }
}

 

 

Solution2：  Iteration(Using a stack or a queue to simulate how DFS works)

 

 

code

class Solution {
    public boolean isSameTree(TreeNode p, TreeNode q) {
        Queue<TreeNode> queue = new LinkedList<>();
        
        queue.add(p);
        queue.add(q);
        
        while(!queue.isEmpty()){
            TreeNode node1 = queue.remove();
            TreeNode node2 = queue.remove();      
            
            if(node1==null && node2 ==null) continue;
            if(node1==null || node2==null) return false;
            if(node1.val != node2.val)  return false;
            
            queue.add(node1.left);
            queue.add(node2.left);
            
            queue.add(node1.right);
            queue.add(node2.right);
        }
        return true;
    }
}