CF1265E Beautiful Mirrors (期望dp 2100)

CF1265E Beautiful Mirrors (期望dp 2100)

• 本博客仅读档代码，好的讲解可以看 jimmywang 的推式子、讲解分析。

代码：

    /*
    * @author:  Snow
    * @Description:  Algorithm Contest
    * @LastEditTime: 2022-08-13 15:17:30
    */
    #include<bits/stdc++.h>
    using namespace std;
    #define int long long 
    #pragma GCC optimize(3)
    #define re register int
    typedef pair<int,int>PII;
    #define pb push_back
    #define mb pop_back
    #define debug(a) cout<<a<<' ';
    #define fer(i,a,b) for(re i=a;i<=b;i++)
    #define der(i,a,b) for(re i=a;i>=b;i--)
    const int N = 2e5+10;
    int a[N];
    const int mod = 998244353;
    int qmi(int a,int b){
        int res=1;
        while(b){
            if(b&1)res=res*a%mod;
            a=a*a%mod;
            b>>=1;
        }
        return res;
    }
    void cf(){
        int n;
        cin>>n;
        for(int i=1;i<=n;i++){
            cin>>a[i];
        }
        int res=1;
        int ans=0;
        for(int i=n;i>=1;i--){
            int x=res*100%mod*qmi(a[i],mod-2)%mod;
            ans=(ans+x)%mod;
            res=x;
        }
        cout<<ans<<endl;
    }
    signed main(){
        ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
        int _=1;
        // cin>>_;
        while(_--){
            cf();
        }
        return 0;
    }