Beautiful Mirrors【Codeforces 1265 E】【期望DP】

Codeforces Round #604 (Div. 2) E

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  题记——不是杭电今年份的原题嘛？为什么比赛的时候没想到这个方面呢？（当然题也读错了，尬……）

杭电多校原题

  然后再继续说一下这道题的特殊之处吧。（随便说说，典型问题，没有特殊之处）

大概画了个图，应该就是可以的吧。

#include <iostream>
#include <cstdio>
#include <cmath>
#include <string>
#include <cstring>
#include <algorithm>
#include <limits>
#include <vector>
#include <stack>
#include <queue>
#include <set>
#include <map>
#include <unordered_map>
#include <unordered_set>
#define lowbit(x) ( x&(-x) )
#define pi 3.141592653589793
#define e 2.718281828459045
#define INF 0x3f3f3f3f
#define HalF (l + r)>>1
#define lsn rt<<1
#define rsn rt<<1|1
#define Lson lsn, l, mid
#define Rson rsn, mid+1, r
#define QL Lson, ql, qr
#define QR Rson, ql, qr
#define myself rt, l, r
#define Min3(a, b, c) min(a, min(b, c))
using namespace std;
typedef unsigned long long ull;
typedef unsigned int uit;
typedef long long ll;
const ll mod = 998244353;
inline ll fast_mi(ll a, ll b = mod - 2)
{
    ll ans = 1;
    while(b)
    {
        if(b & 1)
        {
            ans = ans * a % mod;
        }
        a = a * a % mod;
        b >>= 1;
    }
    return ans;
}
const int maxN = 2e5 + 7;
ll dp[maxN];    //第i天开心的期望天数
int N;
ll p[maxN];
int main()
{
    scanf("%d", &N);
    for(int i=1; i<=N; i++) scanf("%lld", &p[i]);
    dp[0] = 0;
    for(int i=1; i<=N; i++)
    {
        dp[i] = (dp[i - 1] + 1LL) * 100 % mod * fast_mi(p[i]) % mod;
    }
    printf("%lld\n", dp[N]);
    return 0;
}