Submission #1008145

#	Time	Username	Problem	Language	Result	Execution time	Memory
1008145		GrindMachine	Flight to the Ford (BOI22_communication)	C++17	74 / 100	3116 ms	3616 KiB

communication

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;

template<typename T> using Tree = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
typedef long long int ll;
typedef long double ld;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;

#define fastio ios_base::sync_with_stdio(false); cin.tie(NULL)
#define pb push_back
#define endl '\n'
#define sz(a) (int)a.size()
#define setbits(x) __builtin_popcountll(x)
#define ff first
#define ss second
#define conts continue
#define ceil2(x,y) ((x+y-1)/(y))
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define yes cout << "Yes" << endl
#define no cout << "No" << endl

#define rep(i,n) for(int i = 0; i < n; ++i)
#define rep1(i,n) for(int i = 1; i <= n; ++i)
#define rev(i,s,e) for(int i = s; i >= e; --i)
#define trav(i,a) for(auto &i : a)

template<typename T>
void amin(T &a, T b) {
    a = min(a,b);
}

template<typename T>
void amax(T &a, T b) {
    a = max(a,b);
}

#ifdef LOCAL
#include "debug.h"
#else
#define debug(...) 42
#endif

/*

read some solutions a long time ago, remember some key ideas from there

*/

const int MOD = 1e9 + 7;
const int N = 1e5 + 5;
const int inf1 = int(1e9) + 5;
const ll inf2 = ll(1e18) + 5;

#include "communication.h"
//
// --- Sample implementation for the task communication ---
//
// To compile this program with the sample grader, place:
//     communication.h communication_sample.cpp sample_grader.cpp
// in a single folder, then open the terminal in this directory (right-click onto an empty spot in the directory,
// left click on "Open in terminal") and enter e.g.:
//     g++ -std=c++17 communication_sample.cpp sample_grader.cpp
// in this folder. This will create a file a.out in the current directory which you can execute from the terminal
// as ./a.out
// See task statement or sample_grader.cpp for the input specification
//

void encode(int n, int k) {
    int currn = 1;
    while(currn <= n){
        currn <<= 1;
    }

    n = currn;
    mt19937 rng(n);
    int xo = rng()%n;
    k--;
    k ^= xo;
    k++;

    vector<int> a = {0,6,9,15};
    vector<vector<int>> possible(4);

    rep(i,4){
        int x = a[i];
        rep(mask,1<<4){
            int pb = -1;
            bool ok = true;

            rep(bit,4){
                int b = 0;
                if(mask&(1<<bit)) b = 1;
                if(b == 1 and pb == 1){
                    ok = false;
                }
                pb = b;
            }

            if(ok){
                possible[i].pb(x^mask);
            }
        }
    }

    map<int,int> mp;
    mp[1] = 0, mp[n+1] = 0;

    auto range_add = [&](int l, int r, int x){
        mp[l] += x, mp[r+1] -= x;
    };

    auto cnt_zero = [&](){
        vector<pii> b(all(mp));
        int sum = 0;
        int cnt = 0;

        rep(i,sz(b)-1){
            sum += b[i].ss;
            if(sum == 0){
                int len = b[i+1].ff-b[i].ff;
                cnt += len;        
            }    
        }

        return cnt;
    };

    auto kth_zero = [&](int k){
        vector<pii> b(all(mp));
        int sum = 0;

        rep(i,sz(b)-1){
            sum += b[i].ss;
            if(sum == 0){
                int len = b[i+1].ff-b[i].ff;
                if(k <= len){
                    return b[i].ff+k-1;
                }
                else{
                    k -= len;
                }
            }    
        }

        assert(0);
        return -1;
    };

    auto my_send = [&](int i){
        int x = a[i], y = 0;
        rep(bit,4){
            int b = 0;
            if(x&(1<<bit)) b = 1;
            int sent = send(b);
            y |= sent*(1<<bit);
        }
        
        return y;
    };

    while(true){
        int active = cnt_zero();
        if(active <= 2) break;

        vector<int> lens;
        int s1 = active/4, c1 = 4;
        int s2 = ceil2(active,4), c2 = active%4;
        c1 -= c2;
        rep(i,c1) lens.pb(s1);
        rep(i,c2) lens.pb(s2);
        vector<pii> ranges;
        int z = 0;

        rep(i,4){
            int len = lens[i];
            if(!len){
                ranges.pb({0,0});
            }    
            else{
                int l = kth_zero(z+1), r = kth_zero(z+len);
                z += len;
                ranges.pb({l,r});
            }
        }

        int to_send = -1;

        rep(i,4){
            auto [l,r] = ranges[i];
            if(l <= k and r >= k){
                to_send = i;
            }
        }

        int x = my_send(to_send);

        vector<int> bad;
        rep(i,4){
            if(!count(all(possible[i]),x)){
                bad.pb(i);
            }
        }

        trav(i,bad){
            if(ranges[i].ff == -1) conts;
            range_add(ranges[i].ff,ranges[i].ss,1);
        }
    }
}

std::pair<int, int> decode(int n) {
    int currn = 1;
    while(currn <= n){
        currn <<= 1;
    }

    int on = n;
    n = currn;
    mt19937 rng(n);
    int xo = rng()%n;

    vector<int> a = {0,6,9,15};
    vector<vector<int>> possible(4);

    rep(i,4){
        int x = a[i];
        rep(mask,1<<4){
            int pb = -1;
            bool ok = true;

            rep(bit,4){
                int b = 0;
                if(mask&(1<<bit)) b = 1;
                if(b == 1 and pb == 1){
                    ok = false;
                }
                pb = b;
            }

            if(ok){
                possible[i].pb(x^mask);
            }
        }
    }

    map<int,int> mp;
    mp[1] = 0, mp[n+1] = 0;

    auto range_add = [&](int l, int r, int x){
        mp[l] += x, mp[r+1] -= x;
    };

    auto cnt_zero = [&](){
        vector<pii> b(all(mp));
        int sum = 0;
        int cnt = 0;

        rep(i,sz(b)-1){
            sum += b[i].ss;
            if(sum == 0){
                int len = b[i+1].ff-b[i].ff;
                cnt += len;        
            }    
        }

        return cnt;
    };

    auto kth_zero = [&](int k){
        vector<pii> b(all(mp));
        int sum = 0;

        rep(i,sz(b)-1){
            sum += b[i].ss;
            if(sum == 0){
                int len = b[i+1].ff-b[i].ff;
                if(k <= len){
                    return b[i].ff+k-1;
                }
                else{
                    k -= len;
                }
            }    
        }

        assert(0);
        return -1;
    };

    auto my_receive = [&](){
        int x = 0;
        rep(bit,4){
            x = x<<1|receive();
        }
        return x;
    };

    while(true){
        int active = cnt_zero();
        if(active <= 2) break;

        vector<int> lens;
        int s1 = active/4, c1 = 4;
        int s2 = ceil2(active,4), c2 = active%4;
        c1 -= c2;
        rep(i,c1) lens.pb(s1);
        rep(i,c2) lens.pb(s2);
        vector<pii> ranges;
        int z = 0;

        rep(i,4){
            int len = lens[i];
            if(!len){
                ranges.pb({0,0});
            }    
            else{
                int l = kth_zero(z+1), r = kth_zero(z+len);
                z += len;
                ranges.pb({l,r});
            }
        }

        int x = my_receive();

        vector<int> bad;
        rep(i,4){
            if(!count(all(possible[i]),x)){
                bad.pb(i);
            }
        }

        trav(i,bad){
            if(ranges[i].ff == -1) conts;
            range_add(ranges[i].ff,ranges[i].ss,1);
        }
    }

    int active = cnt_zero();
    pii res = {0,0};
    res.ff = kth_zero(1);
    res.ss = res.ff;

    if(active == 2){
        res.ss = kth_zero(2);
    }

    res.ff--, res.ss--;
    res.ff ^= xo, res.ss ^= xo;
    res.ff++, res.ss++;

    if(res.ff > on) res.ff = 1;
    if(res.ss > on) res.ss = 1;

    return res;
}

• Subtask 1: 15 / 15
• Subtask 2: 59.00003 / 85