Graph Theory

Little Q loves playing with different kinds of graphs very much. One day he thought about an interesting category of graphs called ``Cool Graph'', which are generated in the following way:
Let the set of vertices be {1, 2, 3, ..., $n$}. You have to consider every vertice from left to right (i.e. from vertice 2 to $n$). At vertice $i$, you must make one of the following two decisions:
(1) Add edges between this vertex and all the previous vertices (i.e. from vertex 1 to $i-1$).
(2) Not add any edge between this vertex and any of the previous vertices.
In the mathematical discipline of graph theory, a matching in a graph is a set of edges without common vertices. A perfect matching is a matching that each vertice is covered by an edge in the set.
Now Little Q is interested in checking whether a ''Cool Graph'' has perfect matching. Please write a program to help him.

The first line of the input contains an integer $T(1\leq T\leq50)$, denoting the number of test cases.
In each test case, there is an integer $n(2\leq n\leq 100000)$ in the first line, denoting the number of vertices of the graph.
The following line contains $n-1$ integers $a_2,a_3,...,a_n(1\leq a_i\leq 2)$, denoting the decision on each vertice.

For each test case, output a string in the first line. If the graph has perfect matching, output ''Yes'', otherwise output ''No''.

3
2
1
2
2
4
1 1 2

Yes
No
No

2017中国大学生程序设计竞赛 - 女生专场