[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;
     }
 }