oj.uz

Submission #749618

# Submission time Handle Problem Language Result Execution time Memory
749618 2023-05-28T10:06:18 Z anhduc2701 Alternating Current (BOI18_alternating) C++17
0 / 100
 121 ms 109664 KB 
/*
#pragma GCC optimize("Ofast")
#pragma GCC target("avx,avx2,fma")
#pragma GCC optimize("unroll-loops")
*/
#include <bits/stdc++.h>
using namespace std;
#define all(x) x.begin(), x.end()
#define len(x) ll(x.size())
#define eb emplace_back
#define PI acos(-1.0)
#define fi first
#define se second
#define mp make_pair
#define pb push_back
#define MIN(v) *min_element(all(v))
#define MAX(v) *max_element(all(v))
#define BIT(x, i) (1 & ((x) >> (i)))
#define MASK(x) (1LL << (x))
#define task "tnc"
#define rep(i, n) for (int i = 0; i < (n); i++)
#define rep1(i, n) for (int i = 1; i <= (n); i++)
typedef long long ll;
typedef long double ld;
const ll INF = 1e18;
const int maxn = 1e6 + 5;
const int mod = 1e9 + 7;
const int mo = 998244353;
using pi = pair<ll, ll>;
using vi = vector<ll>;
using pii = pair<pair<ll, ll>, ll>;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
struct seg
{
    int l, r, id;
    seg() {}
    seg(int _l, int _r, int _id)
    {
        l = _l;
        r = _r;
        id = _id;
    }
} A[maxn];
int pref[maxn];
vector<int> G[maxn];
int n, m;
int pref1[maxn];
vector<int> sus[maxn];
int col[maxn];
int ch = 0;
void dfs(int u)
{
    for (auto v : G[u])
    {
        if (col[v] == -1)
        {
            col[v] = col[u] ^ 1;
            dfs(v);
        }
        else if (col[v] != col[u] ^ 1)
        {
            ch = 1;
        }
    }
}
int pref2[maxn];
vector<pair<int, int>> st[maxn];
vector<int> era[maxn];
signed main()
{
    cin.tie(0), cout.tie(0)->sync_with_stdio(0);
    cin >> n >> m;
    for (int i = 1; i <= m; i++)
    {
        int l, r;
        cin >> l >> r;
        st[l].pb({r, i});
        pref[l]++;
        pref[r + 1]--;
        if (l > r)
            pref[1]++;
        A[i] = seg(l, r, i);
    }
    vector<int> check;
    for (int i = 1; i <= n; i++)
    {
        pref[i] += pref[i - 1];
        pref1[i] = pref1[i - 1];
        if (pref[i] == 2)
        {
            check.pb(i);
            pref1[i]++;
        }
        if (pref[i] == 1)
        {
            cout << "impossible\n";
            return 0;
        }
    }
    for (int i = 1; i <= n; i++)
    {
        if (A[i].l <= A[i].r)
        {
            if (pref1[A[i].r] - pref1[A[i].l - 1] > 0)
            {
                int v = lower_bound(check.begin(), check.end(), A[i].l) - check.begin();
                while (v < check.size() && check[v] <= A[i].r)
                {
                    sus[check[v]].pb(i);
                    v++;
                }
            }
        }
        else
        {
            int v = lower_bound(check.begin(), check.end(), A[i].l) - check.begin();
            while (v < check.size())
            {
                sus[check[v]].pb(i);
                v++;
            }
            v = lower_bound(check.begin(), check.end(), 1) - check.begin();
            while (v < check.size() && check[v] <= A[i].r)
            {
                sus[check[v]].pb(i);
                v++;
            }
        }
    }

    for (auto v : check)
    {
        G[sus[v][0]].pb(sus[v][1]);
        G[sus[v][1]].pb(sus[v][0]);
    }
    memset(col, -1, sizeof(col));
    for (int i = 1; i <= m; i++)
    {
        if (G[i].size() && col[i] == -1)
        {
            col[i] = 0;
            dfs(i);
        }
    }
    if (ch == 1)
    {
        cout << "impossible\n";
        return 0;
    }
    set<pair<int, int>> pq;
    for (int i = 1; i <= m; i++)
    {
        if (col[i] == 1)
        {
            pref2[A[i].l]++;
            pref2[A[i].r + 1]--;
            if (A[i].l > A[i].r)
                pref2[1]++;
        }
        if (col[i] == -1 && A[i].l > A[i].r)
        {
            pq.insert({A[i].r, i});
            era[A[i].r + 1].pb(i);
        }
    }
    for (int i = 1; i <= n; i++)
    {
        pref2[i] += pref2[i - 1];

        int id = 0;
        int r = 0;
        for (auto v : st[i])
        {
            if (col[v.se] == -1)
            {
                if (i > v.fi)
                {
                    pq.insert({v.fi + n, i});
                }
                else
                {
                    pq.insert({v.fi, i});
                    era[v.fi + 1].pb(i);
                }
            }
        }
        for (auto v : era[i])
        {
            pq.erase({i, v});
        }
        if (pref2[i] == 0)
        {
            int id = (*pq.rbegin()).se;
            int r = (*pq.rbegin()).fi;

            col[id] = 1;
            pref2[i + 1]++;
            pref2[r + 1]--;
            if (A[i].l > A[i].r)
            {
                pref2[A[i].l]++;
            }
        }
    }
    for (int i = 1; i <= m; i++)
    {
        if (col[i] == 1)
        {
            cout << 1;
        }
        else
        {
            cout << 0;
        }
    }
}

Compilation message

alternating.cpp: In function 'void dfs(int)':
alternating.cpp:60:25: warning: suggest parentheses around comparison in operand of '^' [-Wparentheses]
   60 |         else if (col[v] != col[u] ^ 1)
      |                  ~~~~~~~^~~~~~~~~
alternating.cpp: In function 'int main()':
alternating.cpp:107:26: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  107 |                 while (v < check.size() && check[v] <= A[i].r)
      |                        ~~^~~~~~~~~~~~~~
alternating.cpp:117:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  117 |             while (v < check.size())
      |                    ~~^~~~~~~~~~~~~~
alternating.cpp:123:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  123 |             while (v < check.size() && check[v] <= A[i].r)
      |                    ~~^~~~~~~~~~~~~~
alternating.cpp:170:13: warning: unused variable 'id' [-Wunused-variable]
  170 |         int id = 0;
      |             ^~
alternating.cpp:171:13: warning: unused variable 'r' [-Wunused-variable]
  171 |         int r = 0;
      |             ^

Subtask #1
0 / 13.0

# Verdict Execution time Memory Grader output
1 Correct 45 ms 98124 KB Output is correct
2 Correct 49 ms 98184 KB Output is correct
3 Correct 46 ms 98152 KB Output is correct
4 Correct 47 ms 98144 KB Output is correct
5 Correct 48 ms 98120 KB Output is correct
6 Correct 46 ms 98160 KB Output is correct
7 Correct 45 ms 98184 KB Output is correct
8 Correct 44 ms 94188 KB Output is correct
9 Correct 48 ms 98108 KB Output is correct
10 Correct 45 ms 94256 KB Output is correct
11 Correct 44 ms 94172 KB Output is correct
12 Correct 45 ms 98188 KB Output is correct
13 Correct 45 ms 94156 KB Output is correct
14 Correct 45 ms 98132 KB Output is correct
15 Correct 45 ms 98156 KB Output is correct
16 Correct 45 ms 98144 KB Output is correct
17 Correct 47 ms 98092 KB Output is correct
18 Incorrect 45 ms 98188 KB no wires in direction 1 between segments 3 and 3
19 Halted 0 ms 0 KB -

Subtask #2
0 / 20.0

# Verdict Execution time Memory Grader output
1 Correct 45 ms 98124 KB Output is correct
2 Correct 49 ms 98184 KB Output is correct
3 Correct 46 ms 98152 KB Output is correct
4 Correct 47 ms 98144 KB Output is correct
5 Correct 48 ms 98120 KB Output is correct
6 Correct 46 ms 98160 KB Output is correct
7 Correct 45 ms 98184 KB Output is correct
8 Correct 44 ms 94188 KB Output is correct
9 Correct 48 ms 98108 KB Output is correct
10 Correct 45 ms 94256 KB Output is correct
11 Correct 44 ms 94172 KB Output is correct
12 Correct 45 ms 98188 KB Output is correct
13 Correct 45 ms 94156 KB Output is correct
14 Correct 45 ms 98132 KB Output is correct
15 Correct 45 ms 98156 KB Output is correct
16 Correct 45 ms 98144 KB Output is correct
17 Correct 47 ms 98092 KB Output is correct
18 Incorrect 45 ms 98188 KB no wires in direction 1 between segments 3 and 3
19 Halted 0 ms 0 KB -

Subtask #3
0 / 22.0

# Verdict Execution time Memory Grader output
1 Correct 45 ms 98124 KB Output is correct
2 Correct 49 ms 98184 KB Output is correct
3 Correct 46 ms 98152 KB Output is correct
4 Correct 47 ms 98144 KB Output is correct
5 Correct 48 ms 98120 KB Output is correct
6 Correct 46 ms 98160 KB Output is correct
7 Correct 45 ms 98184 KB Output is correct
8 Correct 44 ms 94188 KB Output is correct
9 Correct 48 ms 98108 KB Output is correct
10 Correct 45 ms 94256 KB Output is correct
11 Correct 44 ms 94172 KB Output is correct
12 Correct 45 ms 98188 KB Output is correct
13 Correct 45 ms 94156 KB Output is correct
14 Correct 45 ms 98132 KB Output is correct
15 Correct 45 ms 98156 KB Output is correct
16 Correct 45 ms 98144 KB Output is correct
17 Correct 47 ms 98092 KB Output is correct
18 Incorrect 45 ms 98188 KB no wires in direction 1 between segments 3 and 3
19 Halted 0 ms 0 KB -

Subtask #4
0 / 19.0

# Verdict Execution time Memory Grader output
1 Correct 66 ms 102316 KB Output is correct
2 Correct 66 ms 104088 KB Output is correct
3 Correct 56 ms 96716 KB Output is correct
4 Correct 71 ms 105392 KB Output is correct
5 Correct 121 ms 109440 KB Output is correct
6 Correct 70 ms 98192 KB Output is correct
7 Incorrect 121 ms 109664 KB no wires in direction 0 between segments 1174 and 1174
8 Halted 0 ms 0 KB -

Subtask #5
0 / 26.0

# Verdict Execution time Memory Grader output
1 Correct 45 ms 98124 KB Output is correct
2 Correct 49 ms 98184 KB Output is correct
3 Correct 46 ms 98152 KB Output is correct
4 Correct 47 ms 98144 KB Output is correct
5 Correct 48 ms 98120 KB Output is correct
6 Correct 46 ms 98160 KB Output is correct
7 Correct 45 ms 98184 KB Output is correct
8 Correct 44 ms 94188 KB Output is correct
9 Correct 48 ms 98108 KB Output is correct
10 Correct 45 ms 94256 KB Output is correct
11 Correct 44 ms 94172 KB Output is correct
12 Correct 45 ms 98188 KB Output is correct
13 Correct 45 ms 94156 KB Output is correct
14 Correct 45 ms 98132 KB Output is correct
15 Correct 45 ms 98156 KB Output is correct
16 Correct 45 ms 98144 KB Output is correct
17 Correct 47 ms 98092 KB Output is correct
18 Incorrect 45 ms 98188 KB no wires in direction 1 between segments 3 and 3
19 Halted 0 ms 0 KB -