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.
public class Solution {
public boolean isSameTree(TreeNode p, TreeNode q) {
if(p==null&&q==null)
return true;
if(p==null||q==null) // 若两个都为空的话，则上面一个判断已经返回了true的结果
return false;
return p.val == q.val&&isSameTree(p.left,q.left)&&isSameTree(p.right,q.right);
}
}
