本文介绍了成对的数量的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
从1到K都有N组整数。找出其联合包含所有K元素的对的数量。
我尝试过：
i使用了set_union但它给出了TLE，我该怎么做才能优化它？
There are N sets of integers from 1 to K both inclusive. Find out number of pairs of sets whose union contains all the K elements.
What I have tried:
i have used set_union but its giving TLE , what should i do to optimise it ?
推荐答案
k=5, s1 = {1,2,5}, s2 = {1,4}
，因为 3 是在 s1 和 s2 中都缺少那么你不必完全执行两个集合的联合以发现它们是不好的候选人。
since 3 is missing in both s1 and s2 then you don't have to fully perform the union of the two sets to discover they are bad candidates.
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