Submission #469940

#	Time	Username	Problem	Language	Result	Execution time	Memory
469940		cpp219	Hacker (BOI15_hac)	C++14	100 / 100	79 ms	10692 KiB

hac

#include<bits/stdc++.h>
#define ll int
#define ld long double
#define fs first
#define sc second
#define debug(y) cout<<y,exit(0)
using namespace std;
typedef pair<ll,ll> LL;
const ll N = 1e6 + 9;
const ll mod = 998244353;

ll n,a[N],pre[N],val[N],take,ans;

ll cal(ll l,ll r){
    if (l <= r) return pre[r] - pre[l - 1];
    return pre[r] + pre[n] - pre[l - 1];
}

int main(){
    ios_base::sync_with_stdio(NULL); cin.tie(0); cout.tie(0);
    #define task "test"
    if (fopen(task".inp","r")){
        freopen(task".inp","r",stdin);
        //freopen(task".out","w",stdout);
    }
    cin>>n; take = (n + 1)/2;
    for (ll i = 1;i <= n;i++) cin>>a[i],pre[i] = pre[i - 1] + a[i];
    //cout<<cal(4,1)<<"x"; return 0;
    for (ll i = 1;i <= n;i++){
        ll l = i,r = i + take - 1; if (r > n) r -= n;
        //cout<<l<<" "<<r<<" "<<cal(l,r)<<"\n";
        val[i] = cal(l,r);
    }
    for (ll i = n + 1;i <= 2*n;i++) val[i] = val[i - n];
    //for (ll i = 1;i <= n;i++) cout<<val[i]<<" "; return 0;
    deque<ll> dq;
    for (ll i = 1;i <= 2*n;i++){
        while(!dq.empty() && val[i] <= val[dq.back()]) dq.pop_back();
        while(!dq.empty() && i - dq.front() + 1 > take) dq.pop_front();
        dq.push_back(i);
        if (i >= take) ans = max(ans,val[dq.front()]);
    }
    cout<<ans;
}

/* stuff you should look for
    * int overflow,array bound
    * special cases (n = 1?)
    * do smth instead of nothing and stay organized
    * WRITE STUFF DOWN
    * DON'T GET STUCK ON ONE APPROACH
*/

Compilation message (stderr)

hac.cpp: In function 'int main()':
hac.cpp:23:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   23 |         freopen(task".inp","r",stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 20 / 20
• Subtask 2: 20 / 20
• Subtask 3: 20 / 20
• Subtask 4: 40 / 40