100. Same Tree

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