結果

問題 No.1211 円環はお断り
ユーザー tomatoma
提出日時 2020-08-30 16:32:47
言語 C++17
(gcc 13.3.0 + boost 1.87.0)
結果
AC  
実行時間 497 ms / 2,000 ms
コード長 2,931 bytes
コンパイル時間 2,347 ms
コンパイル使用メモリ 197,372 KB
最終ジャッジ日時 2025-01-14 00:01:23
ジャッジサーバーID
（参考情報） 		judge2 / judge5
このコードへのチャレンジ
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ファイルパターン 結果
sample AC * 2
other AC * 41
権限があれば一括ダウンロードができます

ソースコード

diff # 

#include"bits/stdc++.h"
using namespace std;
#define REP(k,m,n) for(int (k)=(m);(k)<(n);(k)++)
#define rep(i,n) REP((i),0,(n))
using ll = long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using tp3 = tuple<int, int, int>;
using Mat = vector<vector<ll>>;
constexpr int INF = 1 << 28;
constexpr ll INFL = 1ll << 60;
constexpr int dh[4] = { 0,1,0,-1 };
constexpr int dw[4] = { -1,0,1,0 };
bool isin(const int H, const int W, const int h, const int w) {
    return 0 <= h && h < H && 0 <= w && w < W;
}
// ============ template finished ============

ll all(const vector<ll>& A) {
    return accumulate(A.begin(), A.end(), 0ll);
}

vector<ll> make_acc(vector<ll> A) {
    const int N = A.size();
    rep(i, N - 1) {
        A[i + 1] += A[i];
    }
    return A;
}

ll get(const vector<ll>& acc, ll idx) {
    return idx == -1 ? 0 : acc[idx];
}

void update(ll& bestIdx, ll& bestSpan, const ll idx, const ll span) {
    if (span < bestSpan) {
        bestIdx = idx;
        bestSpan = span;
    }
}

ll dist(ll from, ll to) {
    if (from > to) {
        while (true) {
            from++;
            to += from;
        }
    }
    //assert(from <= to);
    from--;
    return to - from;
}

ll need_span(const vector<ll>& acc, const ll idx, const ll val) {
    const ll N = acc.size();
    auto itr = lower_bound(acc.begin(), acc.end(), val);
    if (itr != acc.end()) {
        return dist(idx, itr - acc.begin());
    }
    else {
        ll need = val - acc.back();
        itr = lower_bound(acc.begin(), acc.end(), need);
        return dist(idx, N - 1) + dist(0, itr - acc.begin());
    }
}

pll shortest_span(const vector<ll>& acc, const ll M) {
    const ll N = acc.size();
    ll bestIdx = -1, bestSpan = INF;
    rep(left, N) {
        const ll span = need_span(acc, left, get(acc, left - 1) + M);
        update(bestIdx, bestSpan, left, span);
    }
    return make_pair(bestIdx, bestSpan);
}

bool canCycle(const vector<ll>& acc, ll idx, const ll K, const ll M) {
    const ll N = acc.size();
    ll step = 0;
    rep(_, K) {
        ll span = need_span(acc, idx, get(acc, idx - 1) + M);
        step += span;
        (idx += span) %= N;
    }
    return step <= N;
}

bool judge(const vector<ll>& A, const ll K, const ll M) {
    const ll N = A.size();
    auto acc = make_acc(A);
    const auto[startIdx, span] = shortest_span(acc, M);
    assert(span < N / K + 3);
    for (int i = 0, idx = startIdx; i < span; i++, (++idx) %= N) {
        if (canCycle(acc, idx, K, M)) {
            return true;
        }
    }
    return false;
}

int main()
{
    ll N, K;
    cin >> N >> K;
    vector<ll> A(N);
    rep(i, N)cin >> A[i];

    if (K == 1) {
        cout << all(A) << endl;
        return 0;
    }

    ll safe = 0, out = all(A) / K + 1;
    while (abs(safe - out) > 1) {
        ll mid = (safe + out) / 2;
        (judge(A, K, mid) ? safe : out) = mid;
    }
    cout << safe << endl;
    return 0;
}
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