8. Let $n \in \mathbf{N}^{\cdot}, n \geqslant 2$. The array of positive integers $\left(a_{1}, a_{2}, \cdots, a_{n}\right)$ satisfies:
$$a_{1}+a_{2}+\cdots+a_{n}=2 n$$

If it is not possible to divide $a_{1}, a_{2}, \cdots, a_{n}$ into two groups with equal sums, then $\left(a_{1}, a_{2}, \cdots, a_{n}\right)$ is called "good". Find all "good" arrays.
8. Let $\left(a_{1}, a_{2}, \cdots, a_{n}\right)$ be a "good" array. For $1 \leqslant i \leqslant n$, consider the following $n+1$ numbers:
$$a_{i}, a_{i+1}, a_{i}+a_{i+1}, \cdots, a_{i}+a_{i+1}+\cdots+a_{i+n-1},$$

where $a_{n+j}=a_{j}$.
Since $a_{1}, a_{2}, \cdots, a_{n}$ cannot be divided into two groups with equal sums, i.e., there are no several numbers among them whose sum equals $n$, therefore, in (6), except for $a_{i}, a_{i+1}$, any two of the remaining terms are not congruent modulo $n$ (otherwise, the difference between the larger sum and the smaller sum would equal $n$). Since (6) contains $n+1$ numbers, there must be two numbers that are congruent modulo $n$, so, $a_{i} \equiv a_{i+1}(\bmod n)$. This holds for $i=1,2, \cdots, n$, hence
$$a_{1} \equiv a_{2} \equiv \cdots \equiv a_{n}(\bmod n)$$

Combining this with $a_{1}+a_{2}+\cdots+a_{n}=2 n$, we have
$$a_{1} \equiv a_{2} \equiv \cdots \equiv a_{n} \equiv 1 \text { or } 2(\bmod n),$$

Thus, $\left(a_{1}, a_{2}, \cdots, a_{n}\right)=(1,1, \cdots, 1, n+1)$ or $\left(a_{1}, a_{2}, \cdots, a_{n}\right)=(2,2, \cdots, 2)$ (this is only valid when $n$ is odd), and these arrays clearly meet the requirements.

In summary, when $n$ is odd, $a_{1}, a_{2}, \cdots, a_{n}$ are either one $n+1$ and the rest are 1, or $a_{1}=a_{2}=\cdots=a_{n}=2$; when $n$ is even, $a_{1}, a_{2}, \cdots, a_{n}$ have exactly one $n+1$ and the rest are 1.