Submission #699233

#	Time	Username	Problem	Language	Result	Execution time	Memory
699233		maomao90	Joker (BOI20_joker)	C++17	0 / 100	421 ms	262144 KiB

Joker

// Hallelujah, praise the one who set me free
// Hallelujah, death has lost its grip on me
// You have broken every chain, There's salvation in your name
// Jesus Christ, my living hope
#include <bits/stdc++.h> 
using namespace std;

#define REP(i, s, e) for (int i = (s); i < (e); i++)
#define RREP(i, s, e) for (int i = (s); i >= (e); i--)
template <class T>
inline bool mnto(T& a, T b) {return a > b ? a = b, 1 : 0;}
template <class T>
inline bool mxto(T& a, T b) {return a < b ? a = b, 1: 0;}
typedef long long ll;
typedef long double ld;
#define FI first
#define SE second
typedef pair<int, int> ii;
typedef pair<ll, ll> pll;
typedef tuple<int, int, int> iii;
#define ALL(_a) _a.begin(), _a.end()
#define SZ(_a) (int) _a.size()
#define pb push_back
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<ii> vii;
typedef vector<iii> viii;

#ifndef DEBUG
#define cerr if (0) cerr
#endif

const int INF = 1000000005;
const ll LINF = 1000000000000000005ll;
const int MAXN = 200005;

int n, m, q;
int u[MAXN], v[MAXN];
vii ql[MAXN];

int p[MAXN], rnk[MAXN];
bool col[MAXN];
viii undostk;
void init() {
    undostk.clear();
    REP (i, 1, n + 1) {
        p[i] = i;
        rnk[i] = 1;
        col[i] = 0;
    }
}
ii findp(int u) {
    if (p[u] == u) {
        return {u, 0};
    }
    auto [tp, c] = findp(p[u]);
    return {tp, c ^ col[u]};
}
bool join(int a, int b) {
    auto [pa, ca] = findp(a);
    auto [pb, cb] = findp(b);
    if (pa == pb) {
        if (ca == cb) {
            return 0;
        }
        undostk.pb({-1, -1, -1});
        return 1;
    }
    if (rnk[pa] < rnk[pb]) {
        swap(pa, pb);
        swap(a, b);
    }
    bool delta = 0;
    if (rnk[pa] == rnk[pb]) {
        delta = 1;
        rnk[pa]++;
    }
    undostk.pb({pa, pb, delta});
    p[pb] = pa;
    col[pb] = ca == cb;
    return 1;
}
void undo() {
    assert(!undostk.empty());
    auto [pa, pb, delta] = undostk.back(); undostk.pop_back();
    if (pa == -1) {
        return;
    }
    p[pb] = pb;
    col[pb] = 0;
    rnk[pa] -= delta;
}

int main() {
#ifndef DEBUG
    ios::sync_with_stdio(0), cin.tie(0);
#endif
    cin >> n >> m >> q;
    REP (i, 1, m + 1) {
        cin >> u[i] >> v[i];
    }
    init();
    REP (i, 0, q) {
        int l, r; cin >> l >> r;
        //ql[l].pb(r);
        while (!undostk.empty()) {
            undo;
        }
        bool pos = 1;
        REP (j, 1, l) {
            if (!join(u[j], v[j])) {
                pos = 0;
                break;
            }
        }
        if (!pos) {
            cout << "YES\n";
            continue;
        }
        REP (j, r + 1, m + 1) {
            if (!join(u[j], v[j])) {
                pos = 0;
                break;
            }
        }
        if (!pos) {
            cout << "YES\n";
            continue;
        }
        cout << "NO\n";
    }
    return 0;
}

Compilation message (stderr)

Joker.cpp: In function 'int main()':
Joker.cpp:108:13: warning: statement is a reference, not call, to function 'undo' [-Waddress]
  108 |             undo;
      |             ^~~~
Joker.cpp:108:13: warning: statement has no effect [-Wunused-value]

• Subtask 1: 0 / 6
• Subtask 2: 0 / 8
• Subtask 3: 0 / 25
• Subtask 4: 0 / 10
• Subtask 5: 0 / 22
• Subtask 6: 0 / 29