2020-2021 Winter Petrozavodsk Camp, Belarusian SU Contest C题 （DP+位运算）

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code

/*************************************************************************
> File Name: 1.cpp
> Author: Knowledge_llz
> Mail: 925538513@qq.com
> Blog: https://www.cnblogs.com/Knowledge-Pig/ 
************************************************************************/

#include<bits/stdc++.h>
#define LL long long
#define endl '\n'
using namespace std;
const int maxx = 1e6 + 10, mod = 998244353;
LL n, dp[maxx], sum[maxx], ans = 0;
int main(){
    ios::sync_with_stdio(false); cin.tie(0);
#ifndef ONLINE_JUDGE
    freopen("input.in", "r", stdin);
    freopen("output.out","w", stdout);
#endif
    cin >> n;
    dp[0] = sum[0] = 1;
    for(int i = 1;  i <= n; ++i){
        dp[i] = sum[i - 1];
        bool flag = 0;
        for(int j = 22; j >= 0; --j){
            if(i & (1 << j)){
                if(!flag) flag = 1;
                else (dp[i] -= (sum[(1 << (j + 1)) - 1] - sum[(1 << j) - 1])) %= mod;
            }
        }
        sum[i] = (sum[i - 1] + dp[i]) % mod;
        ans = (ans + dp[i]) % mod;
    }
    cout << (ans + mod) % mod << endl;
    return 0;
}