[LeetCode]100. Same tree

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100.  Same tree 
 Here are the root nodes of two binary trees  p  and  q , Write a function to check whether the two trees are the same .

 If two trees are the same in structure , And the nodes have the same value , They are the same .

 

 Example  1：


 Input ：p = [1,2,3], q = [1,2,3]
 Output ：true
 Example  2：


 Input ：p = [1,2], q = [1,null,2]
 Output ：false
 Example  3：


 Input ：p = [1,2,1], q = [1,1,2]
 Output ：false
 

 Tips ：

 The number of nodes on both trees is in the range  [0, 100]  Inside 
-104 <= Node.val <= 104

Method 1：DFS

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

Method 2：BFS

    public boolean isSameTree(TreeNode p, TreeNode q) {
    
        if (p == null && q == null) return true;
        if (p == null || q == null) return false;
        Queue<TreeNode> queue1 = new LinkedList<>();
        Queue<TreeNode> queue2 = new LinkedList<>();
        queue1.offer(p);
        queue2.offer(q);
        while (!queue1.isEmpty()) {
    
            TreeNode currP = queue1.poll();
            TreeNode currQ = queue2.poll();
            if (currP == null && currQ == null) continue;
            if (currP.val != currQ.val) return false;
            TreeNode currPLeft = currP.left;
            TreeNode currPRight = currP.right;
            TreeNode currQLeft = currQ.left;
            TreeNode currQRight = currQ.right;
            if (currPLeft == null ^ currQLeft == null) return false;
            if (currPRight == null ^ currQRight == null) return false;
            if (currPLeft != null) queue1.offer(currPLeft);
            if (currPRight != null) queue1.offer(currPRight);
            if (currQLeft != null) queue2.offer(currQLeft);
            if (currQRight != null) queue2.offer(currQRight);
        }
        return true;
    }