#include <algorithm>
#include <cmath>
#include <cstdio>
using namespace std;
int main()
{
	int n, mine[16];
	double p;
	while (scanf("%d%lf", &n, &p) == 2)
	{
		for (int i = 0; i < n; i++)
			scanf("%d", mine + i);
		sort(mine, mine + n);
		int cur = 1;
		double curp = 1;
		for (int i = 0; i < n; i++)
		{
			curp *= 1 - ((1 - p) * pow(p - 1, mine[i] - cur) + 1) / (2 - p);
			cur = mine[i] + 1;
		}
		printf("%.7f\n", curp);
	}
	return 0;
}

• Re:几乎是O(1)了，不用dp…… (10) Bloodsheder 2016-06-02 23:12:36