题目大意:
一共有n道题,给出n道题每题的正确的概率,求对0,1,,,n道的概率。
分析:
以为要用分数取模,还去补了一下,后面发现,根本不用。。。。。只是要注意一下负数。直接概率dp就行。
代码附上:
#include <iostream>
using namespace std;
#define maxn 2010
#define ll long long
const ll mod = 1e9 + 7;
ll p[maxn];
ll dp[maxn][maxn];
int main(void)
{
int n;
cin >> n;
for (int i = 1; i <= n; i++) cin >> p[i];
dp[0][0] = 1;
for (int i = 1; i <= n; i++) {
dp[i][0] = dp[i - 1][0] * (mod + 1 - p[i]) % mod;
for (int j = 1; j <= i; j++) {
dp[i][j] = dp[i - 1][j] * (mod + 1 - p[i]) % mod + dp[i - 1][j - 1] * p[i] % mod;
}
}
for (int i = 0; i <= n; i++) cout << dp[n][i] % mod << " ";
return 0;
}