100. Same Tree

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);
    }
}