oj.uz

Submission #749645

# Submission time Handle Problem Language Result Execution time Memory
749645 2023-05-28T10:42:19 Z anhduc2701 Alternating Current (BOI18_alternating) C++17
0 / 100
 121 ms 109772 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 <= m; 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;
    int id;
    int su = 0;
    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].r > su)
        {
            su = A[i].r;
            id = i;
        }
    }

    if (su > 0)
    {
        pq.insert({A[id].r, id});
        era[A[id].r + 1].pb(id);
    }
    for (int i = 1; i <= n; i++)
    {
        pref2[i] += pref2[i - 1];

        int id = 0;
        int r = 0;
        for (auto v : era[i])
        {
            pq.erase({i, v});
        }
        for (auto v : st[i])
        {
            if (col[v.se] == -1)
            {

                if (i > v.fi)
                {
                    pq.insert({v.fi + n, v.se});
                }
                else
                {
                    pq.insert({v.fi, v.se});
                    era[v.fi + 1].pb(v.se);
                }
            }
        }
        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[id].l > A[id].r)
            {
                pref2[A[id].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:61:25: warning: suggest parentheses around comparison in operand of '^' [-Wparentheses]
   61 |         else if (col[v] != col[u] ^ 1)
      |                  ~~~~~~~^~~~~~~~~
alternating.cpp: In function 'int main()':
alternating.cpp:108:26: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  108 |                 while (v < check.size() && check[v] <= A[i].r)
      |                        ~~^~~~~~~~~~~~~~
alternating.cpp:118:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  118 |             while (v < check.size())
      |                    ~~^~~~~~~~~~~~~~
alternating.cpp:124:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  124 |             while (v < check.size() && check[v] <= A[i].r)
      |                    ~~^~~~~~~~~~~~~~
alternating.cpp:180:13: warning: unused variable 'id' [-Wunused-variable]
  180 |         int id = 0;
      |             ^~
alternating.cpp:181:13: warning: unused variable 'r' [-Wunused-variable]
  181 |         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 43 ms 98124 KB Output is correct
3 Correct 45 ms 98164 KB Output is correct
4 Correct 44 ms 98100 KB Output is correct
5 Correct 53 ms 98132 KB Output is correct
6 Correct 53 ms 98184 KB Output is correct
7 Correct 44 ms 98120 KB Output is correct
8 Correct 43 ms 94272 KB Output is correct
9 Correct 44 ms 98192 KB Output is correct
10 Correct 42 ms 94160 KB Output is correct
11 Correct 44 ms 94272 KB Output is correct
12 Correct 46 ms 98088 KB Output is correct
13 Correct 44 ms 94272 KB Output is correct
14 Correct 45 ms 98204 KB Output is correct
15 Correct 46 ms 98100 KB Output is correct
16 Correct 45 ms 98064 KB Output is correct
17 Correct 44 ms 98120 KB Output is correct
18 Incorrect 46 ms 98100 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 43 ms 98124 KB Output is correct
3 Correct 45 ms 98164 KB Output is correct
4 Correct 44 ms 98100 KB Output is correct
5 Correct 53 ms 98132 KB Output is correct
6 Correct 53 ms 98184 KB Output is correct
7 Correct 44 ms 98120 KB Output is correct
8 Correct 43 ms 94272 KB Output is correct
9 Correct 44 ms 98192 KB Output is correct
10 Correct 42 ms 94160 KB Output is correct
11 Correct 44 ms 94272 KB Output is correct
12 Correct 46 ms 98088 KB Output is correct
13 Correct 44 ms 94272 KB Output is correct
14 Correct 45 ms 98204 KB Output is correct
15 Correct 46 ms 98100 KB Output is correct
16 Correct 45 ms 98064 KB Output is correct
17 Correct 44 ms 98120 KB Output is correct
18 Incorrect 46 ms 98100 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 43 ms 98124 KB Output is correct
3 Correct 45 ms 98164 KB Output is correct
4 Correct 44 ms 98100 KB Output is correct
5 Correct 53 ms 98132 KB Output is correct
6 Correct 53 ms 98184 KB Output is correct
7 Correct 44 ms 98120 KB Output is correct
8 Correct 43 ms 94272 KB Output is correct
9 Correct 44 ms 98192 KB Output is correct
10 Correct 42 ms 94160 KB Output is correct
11 Correct 44 ms 94272 KB Output is correct
12 Correct 46 ms 98088 KB Output is correct
13 Correct 44 ms 94272 KB Output is correct
14 Correct 45 ms 98204 KB Output is correct
15 Correct 46 ms 98100 KB Output is correct
16 Correct 45 ms 98064 KB Output is correct
17 Correct 44 ms 98120 KB Output is correct
18 Incorrect 46 ms 98100 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 81 ms 106524 KB Output is correct
2 Correct 73 ms 104128 KB Output is correct
3 Correct 52 ms 96716 KB Output is correct
4 Correct 70 ms 105424 KB Output is correct
5 Correct 118 ms 109468 KB Output is correct
6 Correct 66 ms 98224 KB Output is correct
7 Incorrect 121 ms 109772 KB no wires in direction 1 between segments 762 and 762
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 43 ms 98124 KB Output is correct
3 Correct 45 ms 98164 KB Output is correct
4 Correct 44 ms 98100 KB Output is correct
5 Correct 53 ms 98132 KB Output is correct
6 Correct 53 ms 98184 KB Output is correct
7 Correct 44 ms 98120 KB Output is correct
8 Correct 43 ms 94272 KB Output is correct
9 Correct 44 ms 98192 KB Output is correct
10 Correct 42 ms 94160 KB Output is correct
11 Correct 44 ms 94272 KB Output is correct
12 Correct 46 ms 98088 KB Output is correct
13 Correct 44 ms 94272 KB Output is correct
14 Correct 45 ms 98204 KB Output is correct
15 Correct 46 ms 98100 KB Output is correct
16 Correct 45 ms 98064 KB Output is correct
17 Correct 44 ms 98120 KB Output is correct
18 Incorrect 46 ms 98100 KB no wires in direction 1 between segments 3 and 3
19 Halted 0 ms 0 KB -