Submission #408794

#	Time	Username	Problem	Language	Result	Execution time	Memory
408794		rocks03	The short shank; Redemption (BOI21_prison)	C++14	70 / 100	2076 ms	105336 KiB

prison

#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define pii pair<int, int>
#define pll pair<ll, ll>
#define ff first
#define ss second
#define pb push_back
#define SZ(x) ((int)(x).size())
#define all(x) x.begin(), x.end()
#define debug(x) cout << #x << ": " << x << " "
#define nl cout << "\n"
#define rep(i, a, b) for(int i = (a); i <= (b); i++)
#define per(i, a, b) for(int i = (a); i >= (b); i--)
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

const int MAXN = 2e6+100;
int N, D, T, a[MAXN];

vector<int> g[MAXN];
void compute_time(){
    stack<int> st;
    rep(i, 0, N - 1){
        while(!st.empty()){
            int j = st.top();
            if(a[j] + i - j > T) st.pop();
            else break;
        }
        if(a[i] <= T){
            g[i].pb(i);
        } else{
            if(!st.empty()) g[st.top()].pb(i);
        }
        st.push(i);
    }
}

struct Node{
    pii dp = {0, 0}; int lazy = 0;
};
class SegmentTree{
public:
    vector<Node> st;
    void build(int n){
        st = vector<Node>(4 * n);
    }
    void push(int i){
        if(st[i].lazy){
            int cl = 2 * i + 1, cr = 2 * i + 2;
            st[cl].dp.ff += st[i].lazy, st[cl].lazy += st[i].lazy;
            st[cr].dp.ff += st[i].lazy, st[cr].lazy += st[i].lazy;
            st[i].lazy = 0;
        }
    }
    void merge(int i){
        int cl = 2 * i + 1, cr = 2 * i + 2;
        if(st[cl].dp < st[cr].dp){
            st[i].dp = st[cl].dp;
        } else{
            st[i].dp = st[cr].dp;
        }
    }
    void add(int i, int l, int r, int ql, int qr, int k){
        if(ql <= l && r <= qr){
            st[i].dp.ff += k, st[i].lazy += k; return;
        }
        if(qr < l || ql > r) return;
        push(i);
        int m = (l + r) / 2;
        add(2 * i + 1, l, m, ql, qr, k);
        add(2 * i + 2, m + 1, r, ql, qr, k);
        merge(i);
    }
    void set(int i, int l, int r, int p, pii val){
        if(l == r){
            st[i].dp = val; st[i].lazy = 0; return;
        } else{
            push(i);
            int m = (l + r) / 2;
            if(p <= m) set(2 * i + 1, l, m, p, val);
            else set(2 * i + 2, m + 1, r, p, val);
            merge(i);
        }
    }
    pii query(int i, int l, int r, int ql, int qr){
        if(ql <= l && r <= qr){
            return st[i].dp;
        }
        if(qr < l || ql > r) return {INT_MAX, 0};
        push(i);
        int m = (l + r) / 2;
        pii ans1 = query(2 * i + 1, l, m, ql, qr);
        pii ans2 = query(2 * i + 2, m + 1, r, ql, qr);
        if(ans1 < ans2) return ans1;
        else return ans2;
    }
} st;

pii compute_dp(int penalty){
    st.build(N + 1);
    pii ans; int dpN = 0;
    per(i, N - 1, 0){
        for(int j : g[i]){
            st.add(0, 0, N, j + 1, N, +1);
            dpN++;
        }
        pii val = st.query(0, 0, N, i + 1, N);
        val.ff += penalty, val.ss += 1;
        pii val2 = {dpN, 0};
        if(val > val2) val = val2;
        st.set(0, 0, N, i, val);
        if(i == 0) ans = val;
    }
    return ans;
}

void solve(){
    cin >> N >> D >> T;
    rep(i, 0, N - 1) cin >> a[i];
    compute_time();
    int l = -1, r = N + 1;
    while(r - l > 1){
        int m = (l + r) / 2;
        pii ans = compute_dp(m);
        if(ans.ss <= D) r = m;
        else l = m;
    }
    pii ans = compute_dp(r);
    cout << ans.ff - D * r;
}

int main(){
    ios_base::sync_with_stdio(false), cin.tie(nullptr);
    solve();
    return 0;
}

• Subtask 1: 15 / 15
• Subtask 2: 0 / 10
• Subtask 3: 20 / 20
• Subtask 4: 10 / 10
• Subtask 5: 25 / 25
• Subtask 6: 0 / 20