首先考虑本题的$O(n^2)$做法. $Part1$ 对原序列从大到小排序后,考虑每个数字对最终答案的贡献,有第x个数字对答案的贡献十分难以计算,所以考虑计算数字x是集合第K大的方案数,作为数字x对$ans(K)$的贡献,然后对$ans$求前缀和,这样得到了x是集合第1~K大的对答案的贡献 $Part2$考虑计算$ans(K)$只考虑子集合之中第K大的数的贡献,显然有$$ ans(k) = \sum_{i=k}^n {C_{i-1}^{k-1}*2^{n-i}*a(i)} $$( $a(i)$表…

Rikka with Subset Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/65536 K (Java/Others)Total Submission(s): 1846    Accepted Submission(s): 896 Problem Description As we know, Rikka is poor at math. Yuta is worrying about this situation…

Rikka with Subset Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/65536 K (Java/Others)Total Submission(s): 837    Accepted Submission(s): 411 Problem Description As we know, Rikka is poor at math. Yuta is worrying about this situation,…

Problem Description As we know, Rikka is poor at math. Yuta is worrying about this situation, so he gives Rikka some math tasks to practice. There is one of them: Yuta has n positive A1−An and their sum is m. Then for each subset S of A, Yuta calcula…

Rikka with Subset Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/65536 K (Java/Others)Total Submission(s): 1122    Accepted Submission(s): 541 Problem Description As we know, Rikka is poor at math. Yuta is worrying about this situation…

Rikka with Subset Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/65536 K (Java/Others)Total Submission(s): 1442    Accepted Submission(s): 723 Problem Description As we know, Rikka is poor at math. Yuta is worrying about this situation…

Rikka with Subset Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/65536 K (Java/Others) Total Submission(s): 1440    Accepted Submission(s): 721 Problem Description As we know, Rikka is poor at math. Yuta is worrying about this situatio…

As we know, Rikka is poor at math. Yuta is worrying about this situation, so he gives Rikka some math tasks to practice. There is one of them: Yuta has nn positive A1−AnA1−An and their sum is mm. Then for each subset SS of AA, Yuta calculates the sum…

题目链接 Problem Description As we know, Rikka is poor at math. Yuta is worrying about this situation, so he gives Rikka some math tasks to practice. There is one of them: Yuta has n positive A1−An and their sum is m. Then for each subset S of A, Yuta ca…

As we know, Rikka is poor at math. Yuta is worrying about this situation, so he gives Rikka some math tasks to practice. There is one of them: Yuta has n numbers A[1]~A[n] and a number K. For any none empty subset S of the numbers, the value of S is…