An overnight dance in discotheque题解 其实可以看做一道结论题：只将覆盖次数为2的圆放到另一组。 我们可以将结论分解为两部分： 1.将覆盖次数为2的圆放到另一组。 2.不将覆盖次数大于2的圆放到另一组 在图中我们可以看到，覆盖次数为2的圆c3被放到另一空间， 此操作增加的面积为2(S圆c3-(S圆c4+S圆c5)[即S阴影])=2S空 覆盖次数为2的圆，S圆肯定

The crowdedness of the discotheque would never stop our friends from having fun, but a bit more spaciousness won’t hurt, will it? The discotheque can be seen as an infinite xy-plane, in which there a