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.

遞迴實現

public class TreeNode {
        int val;
        TreeNode left;
        TreeNode right;
        TreeNode(int
 
 x) { val = x; }
    }

    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;
    }

時間複雜度：從程式碼中可以看出，需要對兩棵樹都進行遍歷，因此時間複雜度是O(N)