A100 正确使用递归和灵活使用if

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.

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public static boolean isSameTree(TreeNode p, TreeNode q) {        if(p == null && q == null){        return true;    }else if(p == null || q == null){//说明不可能都是null了        return false;    }else if(p.val != q.val){//经过上两个说明都不为空了        return false;    }        boolean isSameTreeLeft = isSameTree(p.left, q.left);    boolean isSameTreeRight = isSameTree(p.right, q.right);     return isSameTreeLeft && isSameTreeRight;}

递归一定要找到合适的出口，只有p，q都不为空的时候再接着递归