Submission #1117872

#	Time	Username	Problem	Language	Result	Execution time	Memory
1117872		whatthemomooofun1729	Tug of War (BOI15_tug)	C++17	0 / 100	3050 ms	5836 KiB

tug

#include <iostream>
#include <algorithm>
#include <utility>
#include <vector>
#include <stack>
#include <map>
#include <queue>
#include <set>
#include <unordered_set>
#include <unordered_map>
#include <cstring>
#include <cmath>
#include <functional>
#include <cassert>
#include <iomanip>
#include <numeric>
#include <bitset>
#include <sstream>
#include <chrono>
#include <random>

#define ff first
#define ss second
#define PB push_back
#define sz(x) int(x.size())
#define rsz resize
#define fch(xxx, yyy) for (auto xxx : yyy) // abusive notation
#define all(x) (x).begin(),(x).end()
#define eps 1e-9

// more abusive notation (use at your own risk):
// #define int ll

using namespace std;
typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using vi = vector<int>;
using vll = vector<ll>;

// debugging
void __print(int x) {std::cerr << x;}
void __print(ll x) {std::cerr << x;} /* remember to uncomment this when not using THE MACRO */
void __print(unsigned x) {std::cerr << x;}
void __print(ull x) {std::cerr << x;}
void __print(float x) {std::cerr << x;}
void __print(double x) {std::cerr << x;}
void __print(ld x) {std::cerr << x;}
void __print(char x) {std::cerr << '\'' << x << '\'';}
void __print(const char *x) {std::cerr << '\"' << x << '\"';}
void __print(const string& x) {std::cerr << '\"' << x << '\"';}
void __print(bool x) {cerr << (x ? "true" : "false");}
template<typename T, typename V> void __print(const pair<T, V> &x) {std::cerr << '{'; __print(x.ff); std::cerr << ", "; __print(x.ss); std::cerr << '}';}
template<typename T> void __print(const T& x) {int f = 0; std::cerr << '{'; for (auto &i: x) std::cerr << (f++ ? ", " : ""), __print(i); std::cerr << "}";}
void _print() {std::cerr << "]\n";}
template <typename T, typename... V> void _print(T t, V... v) {__print(t); if (sizeof...(v)) std::cerr << ", "; _print(v...);}
void println() {std::cerr << ">--------------------<" << endl;}
#ifndef ONLINE_JUDGE
#define debug(x...) cerr << "[" << #x << "] = ["; _print(x)
#else
#define debug(x...)
#endif

// templates
template <class T> bool ckmin(T &a, const T &b) {return b<a ? a = b, 1 : 0;}
template <class T> bool ckmax(T &a, const T &b) {return b>a ? a = b, 1 : 0;}
template <class T> using gr = greater<T>;
template <class T> using vc = vector<T>;
template <class T> using p_q = priority_queue<T>;
template <class T> using pqg = priority_queue<T, vc<T>, gr<T>>;
template <class T1, class T2> using pr = pair<T1, T2>;
mt19937_64 rng_ll(chrono::steady_clock::now().time_since_epoch().count());
int rng(int M) {return (int)(rng_ll()%M);} /*returns any random number in [0, M) */

// const variables
constexpr int INF = (int)2e9;
constexpr int MOD = 998244353;
constexpr long double EPS = (ld)1e-10, PI = 3.1415926535;
constexpr ll LL_INF = (ll)3e18;
constexpr int mod = (int)1e9 + 7;
constexpr ll inverse = 500000004LL; // inverse of 2 modulo 1e9 + 7

void setIO(const string& str) {// fast input/output
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    if (str.empty()) return;
    freopen((str + ".in").c_str(), "r", stdin);
    freopen((str + ".out").c_str(), "w", stdout);
}

const int MAXN = int(3e4) + 5;
const int MAXK = int(40 * MAXN) + 5;
int N, K;
vc<pii> adj[MAXN * 2];
map<pii, vi> mp;
int deg[MAXN * 2], cc[MAXN * 2], edges[MAXN * 2], siz[MAXN * 2];
pii parent[MAXN * 2];
bitset<MAXK> dp[2]; // DP values: use the index trick
vi d;
vc<pii> v;
int sum = 0;
int cycle_end, cycle_start, final_edge;

int solve() {
    int D = sz(d);
    dp[0][d[0] + 20 * N] = dp[0][-d[0] + 20 * N] = true; // base cases
    for (int i = 1; i < D; ++i) {
        for (int j = 0; j <= 40 * N; ++j) {
            dp[1][j] = (j - d[i] >= 0 && dp[0][j - d[i]]) || (j + d[i] <= 40 * N && dp[0][j + d[i]]); // is the same as automatically resetting all of the bit values
            // transitions
        }
        swap(dp[1], dp[0]);
    }
    for (int i = 0; i <= 40 * N; ++i) {
        int sba = i - 20 * N;
        if (dp[0][i] && abs(sba + sum) <= K) { // testing to see if a solution exists
            return 1;
        }
    }
    return 0;
}

void dfs1(int u) {
    fch(to, adj[u]) {
        if (cc[to.ff] != -1) continue;
        cc[to.ff] = cc[u];
        siz[cc[u]]++;
        dfs1(to.ff);
    }
}

void conn_comp() {
    for (int i = 1; i <= 2 * N; ++i) {
        cc[i] = -1;
    }
    for (int i = 1; i <= 2 * N; ++i) {
        if (cc[i] == -1) {
            cc[i] = i;
            siz[i] = 1;
            dfs1(i);
        }
    }
}

bool dfs(int u, int par) {
    //debug(u, par);
    deg[u] = 0;
    fch(to, adj[u]) {
        if (to.ff == par) continue; // skipping edge to parent vertex
        if (deg[to.ff] == 0) {
            cycle_end = u;
            cycle_start = to.ff;
            final_edge = to.ss;
            return true;
        }
        parent[to.ff] = {u, to.ss};
        if (dfs(to.ff, parent[to.ff].ff))
            return true;
    }
    return false;
}

signed main() { // TIME YOURSELF !!!
    setIO("");
    cin >> N >> K;
    for (int i = 0; i < 2 * N; ++i) {
        int l, r, s;
        cin >> l >> r >> s;
        r += N;
        adj[l].PB({r, s});
        adj[r].PB({l, s});
        mp[{l, r}].PB(s);
        deg[l]++, deg[r]++;
        v.PB({l, r});
        parent[i+1] = {-1, -1}; // just setting all of the values in parent[i] to -1
    }
    conn_comp();
    for (int i = 0; i < sz(v); ++i) {
        edges[cc[v[i].ff]]++;
    }
    for (int i = 1; i <= 2 * N; ++i) {
        if (edges[cc[i]] < siz[cc[i]]) {
            cout << "NO";
            return 0;
        }
    }
    for (auto i = mp.begin(); i != mp.end(); i++) {
        if (sz(i->ss) == 2) {
            int A = (i->ss)[0], B = (i->ss)[1];
            d.PB(abs(-A + B));
            deg[(i->ff).ff] = deg[(i->ff).ss] = 0;
        }
    }
    queue<int> q;
    for (int i = 1; i <= 2 * N; ++i) {
        if (sz(adj[i]) == 1) {
            q.push(i);
            deg[i] = 1;
        }
    }
    while (!q.empty()) {
        int u = q.front();
        q.pop();
        fch(to, adj[u]) {
            sum += (u <= N ? -1 : 1) * to.ss;
            deg[to.ff]--;
            if (deg[to.ff] == 1) q.push(to.ff);
        }
    }
    for (int i = 1; i <= 2 * N; ++i) {
        if (deg[i] == 2) {
            int S = 0, bit = 0;
            deg[i] = 0;
            dfs(i, parent[i].ff);
            for (int u = cycle_end; u != cycle_start; u = parent[u].ff, bit ^= 1) {
                S += (bit == 0 ? -1 : 1) * parent[u].ss;
                if (u == cycle_start) break;
            }
            S += (bit == 0 ? -1 : 1) * final_edge;
            d.PB(abs(S));
        }
    }
    cout << (solve() == 1 ? "YES" : "NO");
    return 0;
}

// TLE -> TRY NOT USING DEFINE INT LONG LONG
// CE -> CHECK LINE 45
// 5000 * 5000 size matrices are kinda big (potential mle)
// Do something, start simpler

Compilation message (stderr)

tug.cpp: In function 'void setIO(const string&)':
tug.cpp:89:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   89 |     freopen((str + ".in").c_str(), "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
tug.cpp:90:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   90 |     freopen((str + ".out").c_str(), "w", stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 18
• Subtask 2: 0 / 30
• Subtask 3: 0 / 23
• Subtask 4: 0 / 29