Submission #152092

#	Time	Username	Problem	Language	Result	Execution time	Memory
152092		evpipis	Homecoming (BOI18_homecoming)	C++11	62 / 100	324 ms	116664 KiB

homecoming

#include "homecoming.h"
#include <bits/stdc++.h>
using namespace std;

#define fi first
#define se second
#define mp make_pair
typedef long long ll;
typedef pair<int, int> ii;

const int len = 2e6+5;
const ll inf = 1e17;
int ar[len], br[len], n, k;
ll suf[len], sufa[len], sufb[len], mx[len], dp[len];
deque<pair<int, ll> > deq;

ll fix(int st){
    for (int i = n-1; i >= 0; i--){
        sufa[i] = ar[(st+i)%n] + sufa[i+1];
        sufb[i] = br[(st+i)%n] + sufb[i+1];
    }

    mx[n] = dp[n] = suf[n] = 0;
    for (int i = n-1; i >= 0; i--){
        dp[i] = sufa[i]-sufb[i] + mx[i+1];
        //for (int j = i+1; j <= n+1; j++)
          //  dp[i] = max(dp[i], sufa[i]-sufb[i] + sufb[j+k-1]-sufa[j]+suf[j]);

        suf[i] = max(suf[i+1], dp[i]);
        mx[i] = max(mx[i+1], sufb[i+k-1]-sufa[i]+suf[i]);
    }

    return dp[0];
}

void init(){
    deq.clear();
    for (int i = 0; i <= 2*n; i++)
        sufa[i] = sufb[i] = 0;
}

ll solve(int N, int K, int A[], int B[]){
    n = N, k = K;
    for (int i = 0; i < n; i++){
        ar[i] = A[i];
        br[i] = B[i];
    }

    init();
    int pos = 0;
    ll best = -inf;

    for (int i = 2*n-1; i >= 0; i--){
        sufa[i] = sufa[i+1] + ar[i%n];
        sufb[i] = sufb[i+1] + br[i%n];
    }

    for (int i = 0, j = 1; i < n; i++){
        while (!deq.empty() && deq.front().fi <= i)
            deq.pop_front();
        while (j-i <= n-k+1){
            ll val = sufb[j+k-1]-sufa[j];
            while (!deq.empty() && val > deq.back().se)
                deq.pop_back();
            deq.push_back(mp(j, val));

            j++;
        }

        if (sufa[i]-sufb[i] + deq.front().se > best)
            best = sufa[i]-sufb[i] + deq.front().se, pos = i;
    }

    init();
    return max(0LL, fix(pos));
}

/*
1
3 2
40 80 100
140 0 20
*/

• Subtask 1: 13 / 13
• Subtask 2: 18 / 18
• Subtask 3: 31 / 31
• Subtask 4: 0 / 38