Submission #1245376

#	Time	Username	Problem	Language	Result	Execution time	Memory
1245376		huydayy	Alternating Heights (CCO22_day1problem1)	C++20	0 / 25	104 ms	3544 KiB

Main

#include <bits/stdc++.h>
#define TASK "E"
#define int long long
#define pb push_back
#define FOR(i,a,b) for (int i = a, _b = b; i <= _b; ++i)
#define FAST ios::sync_with_stdio(0); cin.tie(0); cout.tie(0)
using namespace std;

const int MAXN = 3005;
int N, K, Q;
int a[MAXN], ok[MAXN];
vector<int> G[MAXN];
int deg[MAXN];

bool has_cycle() {
    queue<int> q;
    int cnt = 0;
    vector<int> tmp_deg(K + 1);
    FOR(i,1,K) tmp_deg[i] = deg[i];
    FOR(i,1,K) if (tmp_deg[i] == 0) q.push(i);
    while (!q.empty()) {
        int u = q.front(); q.pop();
        ++cnt;
        for (int v : G[u]) {
            if (--tmp_deg[v] == 0)
                q.push(v);
        }
    }
    return cnt < K;
}

void preprocess() {
    int x = 1, y = 1;
    int turn = 1;
    while (x <= N) {
        while (y < N) {
            int u = a[y], v = a[y + 1];
            if (u == v) break;
            if (turn & 1) G[v].pb(u), deg[u]++;
            else G[u].pb(v), deg[v]++;
            if (has_cycle()) {
                // remove last added
                if (turn & 1) G[v].pop_back(), deg[u]--;
                else G[u].pop_back(), deg[v]--;
                break;
            }
            y++;
            turn ^= 1;
        }
        ok[x] = y;
        if (x < y) {
            int u = a[x], v = a[x + 1];
            if (turn & 1) { 
                auto &vec = G[u];
                vec.pop_back();
                deg[v]--;
            } else {
                auto &vec = G[v];
                vec.pop_back();
                deg[u]--;
            }
            turn ^= 1;
        } else {
            y = x + 1;
            turn = 1;
        }
        x++;
    }
}

int32_t main() {
    if (fopen(TASK".inp", "r")) {
        freopen(TASK".inp", "r", stdin);
        freopen(TASK".out", "w", stdout);
    }
    FAST;
    cin >> N >> K >> Q;
    FOR(i, 1, N) cin >> a[i];

    preprocess();

    while (Q--) {
        int x, y; cin >> x >> y;
        cout << (ok[x] >= y ? "YES" : "NO") << '\n';
    }
    return 0;
}

Compilation message (stderr)

Main.cpp: In function 'int32_t main()':
Main.cpp:73:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   73 |         freopen(TASK".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
Main.cpp:74:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   74 |         freopen(TASK".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 4
• Subtask 2: 0 / 6
• Subtask 3: 0 / 7
• Subtask 4: 0 / 8