This paper proposes the concept of adjustable loop and tries to make some rudimentary study of the multiple optimum-solution of minimum cost flow.

本文提出了可调圈的概念，并力图对最小费用流问题的多重最优解进行一些探讨。

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As multiple sequence alignment problem is an NPC problem, so its optimum solution cannot be obtained because of the time and space limits.

多序列比对问题是一个NPC问题，由于时间和空间的限制不能够求出精确解。

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