2017 ccpc final

【文件属性】：
文件名称：2017 ccpc final
文件大小：562KB
文件格式：PDF
更新时间：2021-02-24 19:29:01
ccpc final acm 2017 CCPC Final Contest Onsite Round, Sunday, December 3rd, 2017 Problem A. Dogs and Cages Jerry likes dogs. He has N dogs numbered 0, 1, . . . , N − 1. He also has N cages numbered 0, 1, . . . , N − 1. Everyday he takes all his dogs out and walks them outside. When he is back home, as dogs can’t recognize the numbers, each dog just randomly selects a cage and enters it. Each cage can hold only one dog. One day, Jerry noticed that some dogs were in the cage with the same number of themselves while others were not. Jerry would like to know what’s the expected number of dogs that are NOT in the cage with the same number of themselves.