Submission #752728

#	Time	Username	Problem	Language	Result	Execution time	Memory
752728		GrindMachine	Tug of War (BOI15_tug)	C++17	100 / 100	2112 ms	7984 KiB

tug

// Om Namah Shivaya

#pragma GCC optimize("O3","unroll-loops")
#pragma GCC target("avx2")

#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) 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(x) 42
#endif

/*

refs:
https://github.com/tmwilliamlin168/CompetitiveProgramming/blob/master/BtOI/15-Tug.cpp
https://github.com/nikolapesic2802/Programming-Practice/blob/master/Tug%20of%20War/main.cpp

*/

const int MOD = 1e9 + 7;
const int N = 3e4 + 5;
const int inf1 = int(1e9) + 5;
const ll inf2 = ll(1e18) + 5;

vector<array<ll,3>> adj[N*2];

void solve(int test_case)
{
    ll n,k; cin >> n >> k;
    vector<ll> deg(2*n+5);

    rep1(i,2*n){
        ll u,v,w; cin >> u >> v >> w;
        v += n;
        adj[u].pb({v,w,i});
        adj[v].pb({u,w,i});
        deg[u]++, deg[v]++;
    }

    queue<ll> q;
    vector<bool> vis_node(2*n+5), vis_edge(2*n+5);

    rep1(i,2*n){
        if(deg[i] < 2){
            q.push(i);
        }
    }

    ll diff = 0;

    while(!q.empty()){
        ll u = q.front();
        q.pop();
    
        vis_node[u] = 1;

        if(!deg[u]){
            no;
            return;
        }

        for(auto [v, w, id] : adj[u]){
            if(vis_edge[id]) conts;
            vis_edge[id] = 1;
            deg[v]--;

            if(deg[v] < 2){
                q.push(v);
            }

            if(u <= n) diff += w;
            else diff -= w;
        }
    }

    rep1(u,2*n){
        if(vis_node[u]) conts;
        vector<array<ll,3>> good;

        for(auto [v, w, id] : adj[u]){
            if(vis_node[v]) conts;
            good.pb({v,w,id});
        }

        assert(sz(good) == 2);
        adj[u] = good;
    }

    vector<ll> vals;

    rep1(u,2*n){
        if(vis_node[u]) conts;

        vector<ll> weights;
        ll ptr = u;
        ll prev_id = -1;

        while(true){
            if(ptr == u and prev_id != -1){
                break;
            }

            vis_node[ptr] = 1;

            for(auto [v, w, id] : adj[ptr]){
                if(id == prev_id) conts;
                weights.pb(w);
                ptr = v;
                prev_id = id;
                break;
            }
        }

        ll val = 0;
        rep(i,sz(weights)){
            ll c = -1;
            if(!(i & 1)) c = 1;
            val += c * weights[i];
        }

        val = abs(val);
        vals.pb(val);
    }

    bitset<40*N> dp;
    dp[20*N] = 1;

    trav(x,vals){
        dp = (dp << x) | (dp >> x);
    }

    rep(i,40*N){
        if(dp[i]){
            ll d = i - 20*N;
            ll diff2 = diff + d;
            if(abs(diff2) <= k){
                yes;
                return;
            }
        }
    }

    no;
}

int main()
{
    fastio;

    int t = 1;
    // cin >> t;

    rep1(i, t) {
        solve(i);
    }

    return 0;
}

Compilation message (stderr)

tug.cpp: In function 'void solve(int)':
tug.cpp:33:36: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   33 | #define rep(i, n) for(int i = 0; i < n; ++i)
      |                                    ^
tug.cpp:157:9: note: in expansion of macro 'rep'
  157 |         rep(i,sz(weights)){
      |         ^~~

• Subtask 1: 18 / 18
• Subtask 2: 30 / 30
• Subtask 3: 23 / 23
• Subtask 4: 29 / 29