# Sufficient Condition for Tournament Score Sequences

There are $N$ players, and each player plays a match with everyone else exactly once. There is no tie. Each player's score is the number of matches he wins. What constraints can their scores be?

Is every system of scores in which all scores are between $0$ and $N-1$, the sum of scores equal to $N(N-1)/2$, and at most one $0$ score and at most one $N-1$ score achievable in such a matching setting, or there are actually more constraints? If it is the former, how to prove? If it is the latter, what other constraints will sufficient guarantee the set of scores be valid?

For example, for $4$ players, the set of scores cannot be $(3,3,0,0)$ since there can only be one player who wins 3 games.

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A given non-decreasing sequence of non-negative integers $v_1\leq v_2\leq v_3\cdots\leq v_n$ is a score sequence of a tournament if and only if for each integer $k$ with $1\leq k\leq n$$\sum_{i=1}^kv_i\geq\binom{k}{2}$$ with equality when$k=n\$.