Submission #719663

#	Time	Username	Problem	Language	Result	Execution time	Memory
719663		Jarif_Rahman	Ancient Books (IOI17_books)	C++17	100 / 100	500 ms	46264 KiB

books

#include <bits/stdc++.h>
#define pb push_back
#define f first
#define sc second
using namespace std;
typedef long long int ll;
typedef string str;

struct dsu{
    int n;
    vector<int> sz, p;
    vector<int> &first, &last;
    dsu(int _n, vector<int>& _first, vector<int>& _last): n(_n), first(_first), last(_last){
        sz.resize(n, 1);
        p.resize(n);
        for(int i = 0; i < n; i++) p[i] = i;
    }
    int get(int x){
        if(p[x] != x) p[x] = get(p[x]);
        return p[x];
    }
    void unite(int a, int b){
        a = get(a), b  = get(b);
        if(a == b) return;
        if(sz[b] > sz[a]) swap(a, b);
        sz[a]+=sz[b];
        sz[b] = 0;
        first[a] = min(first[a], first[b]);
        last[a] = max(last[a], last[b]);
        p[b] = a;
    }
};
 
ll minimum_walk(vector<int> p, int s){
    int n = p.size();
    ll ans = 0;
 
    vector<int> C(n, -1), sz;
    int k = 0;
    for(int i = 0; i < n; i++){
        if(C[i] != -1) continue;
        int x = p[i];
        C[i] = k;
        sz.pb(1);
        ans+=abs(i-x);
        while(x != i){
            C[x] = k;
            sz.back()++;
            ans+=abs(p[x]-x);
            x = p[x];
        }
        k++;
    }

    vector<int> first(k, -1), last(k);
    for(int i = 0; i < n; i++){
        if(first[C[i]] == -1) first[C[i]] = i;
        last[C[i]] = i;
    }

    int L, R;
    vector<bool> unnecessary(k, 0);
    for(int i = 0; i < n; i++){
        if(sz[C[i]] > 1 || i == s){
            L = i;
            break;
        }
        unnecessary[C[i]] = 1;
    }
    for(int i = n-1; i >= 0; i--){
        if(sz[C[i]] > 1 || i == s){
            R = i;
            break;
        }
        unnecessary[C[i]] = 1;
    }

    dsu ds(k, first, last);
    vector<int> last_added(k, -1);
    set<int> st;
    for(int i = 0; i < n; i++){
        int c = ds.get(C[i]);
        if(last_added[c] != -1) st.erase(last_added[c]), last_added[c] = -1;
        while(!st.empty() && *prev(st.end()) > first[c]){
            int j = *prev(st.end());
            st.erase(prev(st.end()));
            last_added[ds.get(C[j])] = -1;
            ds.unite(c, C[j]);
        }
        c = ds.get(c);
        if(i == last[c]) continue;
        last_added[c] = i;
        st.insert(i);
    }
    for(int i = n-1; i >= 0; i--){
        int c = ds.get(C[i]);
        if(last_added[c] != -1) st.erase(last_added[c]), last_added[c] = -1;
        while(!st.empty() && *st.begin() < last[c]){
            int j = *st.begin();
            st.erase(st.begin());
            last_added[ds.get(C[j])] = -1;
            ds.unite(c, C[j]);
        }
        c = ds.get(c);
        if(i == first[c]) continue;
        last_added[c] = i;
        st.insert(i);
    }

    for(int &x: C) x = ds.get(x);

    int l = first[C[s]], r = last[C[s]];
    while(l > L || r < R){
        int in = -1;
        ll lx = 0, rx = 0;
        for(int i = l-1; i >= 0; i--){
            if(unnecessary[C[i]]) break;
            if(C[i] == C[i+1]) continue;
            lx+=2;
            if(i != last[C[i]]){
                in = i;
                break;
            }
            i = first[C[i]];
        }
        for(int i = r+1; i < n; i++){
            if(unnecessary[C[i]]) break;
            if(C[i] == C[i-1]) continue;
            rx+=2;
            if(i != first[C[i]]){
                in = i;
                break;
            }
            i = last[C[i]];
        }

        if(in == -1){
            ans+=lx+rx;
            break;
        }
        ans+=min(lx, rx);
        l = first[C[in]], r = last[C[in]];
    }

    return ans;
}

• Subtask 1: 12 / 12
• Subtask 2: 10 / 10
• Subtask 3: 28 / 28
• Subtask 4: 20 / 20
• Subtask 5: 30 / 30