1-2 Reorder

Alice has an array $A$ of length $N$. Every element of $A$ is either $1$ or $2$. Alice will modify the array according to the following process: - First, choose a permutation $P$ of the integers $[1, 2, \ldots, N-1]$. A permutation of the integers $[1, 2, \ldots, N-1]$ is an array of length $N-1$ that contains every integer from $1$ to $N-1$ exactly once. - Then, for each $i$ from $1$ to $N-1$