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Submission #251905

# Submission time Handle Problem Language Result Execution time Memory
251905 2020-07-23T04:48:57 Z jhnah917 Alternating Current (BOI18_alternating) C++14
32 / 100
 215 ms 2048 KB 
#include <bits/stdc++.h>
#define x first
#define y second
#define all(v) v.begin(), v.end()
#define compress(v) sort(all(v)), v.erase(unique(all(v)), v.end())
using namespace std;

typedef long long ll;

struct Info{
    int s, e, x;
    Info() : Info(0, 0, 0) {}
    Info(int s, int e, int x) : s(s), e(e), x(x) {}
    bool operator < (const Info &t) const {
        if(s != t.s) return s < t.s;
        if(e != t.e) return e > t.e;
        return x < t.x;
    }
};

int n, m;
Info a[101010];
int ans[101010];
bool chk[101010][2];

void naive(){
    for(int bit=0; bit<(1 << m); bit++){
        memset(chk, 0, sizeof chk);
        for(int i=1; i<=m; i++){
            int j = i-1;
            for(int k=a[i].s; ; k++){
                if(k > n) k = 1;
                chk[k][(bit >> j) & 1] = 1;
                if(k == a[i].e) break;
            }
        }
        int flag = 1;
        for(int i=1; i<=n; i++) flag &= (chk[i][0] & chk[i][1]);
        if(flag){
            for(int i=0; i<m; i++) cout << ((bit >> i) & 1);
            return;
        }
    }
    cout << "impossible";
}

vector<int> big;
int par[1010];

int find(int v){ return v == par[v] ? v : par[v] = find(par[v]); }
void partition(){
    vector<Info> v; int ed = 0, idx = 0;
    for(int i=1; i<=m; i++){
        v.push_back(a[i]);
        if(a[i].s > a[i].e){
            ed = max(ed, a[i].e);
            if(ed == a[i].e) idx = i;
            v.back().e += n;
        }
    }
    sort(all(v));
    deque<Info> dq;
    iota(par, par+1010, 0);
    for(auto i : v){
        if(dq.empty() || dq.back().e < i.e) dq.push_back(i);
        else par[i.x] = dq.back().x;
    }
    while(dq.size() && dq.front().e <= ed) par[dq.front().x] = idx, dq.pop_front();
    for(auto i : dq) big.push_back(i.x);
    compress(big);
    for(int i=1; i<=m; i++) par[i] = find(par[i]);
}

int even(){
    int pv = 0;
    for(auto i : big){
        ans[i] = (pv & 1); pv++;
    }
    for(int i=1; i<=m; i++){
        if(i == par[i]) continue;
        ans[i] = !ans[par[i]];
    }
    for(int i=1; i<=m; i++){
        int s = a[i].s, e = a[i].e;
        for(int j=s; ; j++){
            if(j > n) j = 1;
            chk[j][ans[i]] = 1;
            if(j == e) break;
        }
    }
    for(int i=1; i<=n; i++){
        if(!chk[i][0] || !chk[i][1]) return 0;
    }
    for(int i=1; i<=m; i++) cout << ans[i];
    return 1;
}

void subtask55(){
    partition();
    if(even()) return;
    big.push_back(big[0]);
    big.erase(big.begin());
    memset(chk, 0, sizeof chk);
    if(!even()) cout << "impossible";
}

int main(){
    ios_base::sync_with_stdio(false); cin.tie(nullptr);
    cin >> n >> m;
    for(int i=1; i<=m; i++){ cin >> a[i].s >> a[i].e; a[i].x = i; }
    if(n <= 15 && m <= 15){ naive(); return 0; }
    if(n <= 1000 && m <= 1000){ subtask55(); return 0; }
    sort(a+1, a+m+1);
    int cnt0 = 0, cnt1 = 0;
    for(int i=1; i<=m; i++){
        int s = a[i].s, e = a[i].e, x = a[i].x;
        if(cnt0 < cnt1){
            if(cnt0 >= s-1) cnt0 = max(cnt0, e), ans[x] = 0;
        }else{
            if(cnt1 >= s-1) cnt1 = max(cnt1, e), ans[x] = 1;
        }
    }
    if(cnt0 < n || cnt1 < n){
        cout << "impossible"; return 0;
    }
    for(int i=1; i<=m; i++) cout << ans[i];
}

Subtask #1
13.0 / 13.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 1664 KB Output is correct
2 Correct 1 ms 1664 KB Output is correct
3 Correct 1 ms 1664 KB Output is correct
4 Correct 2 ms 1664 KB Output is correct
5 Correct 1 ms 1664 KB Output is correct
6 Correct 1 ms 1664 KB Output is correct
7 Correct 1 ms 1664 KB Output is correct
8 Correct 2 ms 1664 KB Output is correct
9 Correct 1 ms 1664 KB Output is correct
10 Correct 4 ms 1664 KB Output is correct
11 Correct 2 ms 1664 KB Output is correct
12 Correct 2 ms 1664 KB Output is correct
13 Correct 13 ms 1664 KB Output is correct
14 Correct 1 ms 1664 KB Output is correct
15 Correct 1 ms 1664 KB Output is correct
16 Correct 25 ms 1664 KB Output is correct
17 Correct 4 ms 1664 KB Output is correct
18 Correct 4 ms 1792 KB Output is correct
19 Correct 1 ms 1664 KB Output is correct
20 Correct 1 ms 1664 KB Output is correct
21 Correct 1 ms 1664 KB Output is correct
22 Correct 21 ms 1664 KB Output is correct
23 Correct 1 ms 1664 KB Output is correct
24 Correct 3 ms 1664 KB Output is correct
25 Correct 1 ms 1664 KB Output is correct
26 Correct 1 ms 1664 KB Output is correct
27 Correct 24 ms 1664 KB Output is correct
28 Correct 1 ms 1664 KB Output is correct
29 Correct 2 ms 1664 KB Output is correct
30 Correct 2 ms 1792 KB Output is correct
31 Correct 1 ms 1664 KB Output is correct
32 Correct 1 ms 1664 KB Output is correct
33 Correct 1 ms 1664 KB Output is correct
34 Correct 1 ms 1664 KB Output is correct
35 Correct 201 ms 1664 KB Output is correct
36 Correct 8 ms 1664 KB Output is correct
37 Correct 2 ms 1664 KB Output is correct
38 Correct 215 ms 1780 KB Output is correct
39 Correct 2 ms 1664 KB Output is correct
40 Correct 2 ms 1664 KB Output is correct

Subtask #2
0 / 20.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 1664 KB Output is correct
2 Correct 1 ms 1664 KB Output is correct
3 Correct 1 ms 1664 KB Output is correct
4 Correct 2 ms 1664 KB Output is correct
5 Correct 1 ms 1664 KB Output is correct
6 Correct 1 ms 1664 KB Output is correct
7 Correct 1 ms 1664 KB Output is correct
8 Correct 2 ms 1664 KB Output is correct
9 Correct 1 ms 1664 KB Output is correct
10 Correct 4 ms 1664 KB Output is correct
11 Correct 2 ms 1664 KB Output is correct
12 Correct 2 ms 1664 KB Output is correct
13 Correct 13 ms 1664 KB Output is correct
14 Correct 1 ms 1664 KB Output is correct
15 Correct 1 ms 1664 KB Output is correct
16 Correct 25 ms 1664 KB Output is correct
17 Correct 4 ms 1664 KB Output is correct
18 Correct 4 ms 1792 KB Output is correct
19 Correct 1 ms 1664 KB Output is correct
20 Correct 1 ms 1664 KB Output is correct
21 Correct 1 ms 1664 KB Output is correct
22 Correct 21 ms 1664 KB Output is correct
23 Correct 1 ms 1664 KB Output is correct
24 Correct 3 ms 1664 KB Output is correct
25 Correct 1 ms 1664 KB Output is correct
26 Correct 1 ms 1664 KB Output is correct
27 Correct 24 ms 1664 KB Output is correct
28 Correct 1 ms 1664 KB Output is correct
29 Correct 2 ms 1664 KB Output is correct
30 Correct 2 ms 1792 KB Output is correct
31 Correct 1 ms 1664 KB Output is correct
32 Correct 1 ms 1664 KB Output is correct
33 Correct 1 ms 1664 KB Output is correct
34 Correct 1 ms 1664 KB Output is correct
35 Correct 201 ms 1664 KB Output is correct
36 Correct 8 ms 1664 KB Output is correct
37 Correct 2 ms 1664 KB Output is correct
38 Correct 215 ms 1780 KB Output is correct
39 Correct 2 ms 1664 KB Output is correct
40 Correct 2 ms 1664 KB Output is correct
41 Correct 1 ms 1536 KB Output is correct
42 Incorrect 1 ms 1664 KB 'impossible' claimed, but there is a solution
43 Halted 0 ms 0 KB -

Subtask #3
0 / 22.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 1664 KB Output is correct
2 Correct 1 ms 1664 KB Output is correct
3 Correct 1 ms 1664 KB Output is correct
4 Correct 2 ms 1664 KB Output is correct
5 Correct 1 ms 1664 KB Output is correct
6 Correct 1 ms 1664 KB Output is correct
7 Correct 1 ms 1664 KB Output is correct
8 Correct 2 ms 1664 KB Output is correct
9 Correct 1 ms 1664 KB Output is correct
10 Correct 4 ms 1664 KB Output is correct
11 Correct 2 ms 1664 KB Output is correct
12 Correct 2 ms 1664 KB Output is correct
13 Correct 13 ms 1664 KB Output is correct
14 Correct 1 ms 1664 KB Output is correct
15 Correct 1 ms 1664 KB Output is correct
16 Correct 25 ms 1664 KB Output is correct
17 Correct 4 ms 1664 KB Output is correct
18 Correct 4 ms 1792 KB Output is correct
19 Correct 1 ms 1664 KB Output is correct
20 Correct 1 ms 1664 KB Output is correct
21 Correct 1 ms 1664 KB Output is correct
22 Correct 21 ms 1664 KB Output is correct
23 Correct 1 ms 1664 KB Output is correct
24 Correct 3 ms 1664 KB Output is correct
25 Correct 1 ms 1664 KB Output is correct
26 Correct 1 ms 1664 KB Output is correct
27 Correct 24 ms 1664 KB Output is correct
28 Correct 1 ms 1664 KB Output is correct
29 Correct 2 ms 1664 KB Output is correct
30 Correct 2 ms 1792 KB Output is correct
31 Correct 1 ms 1664 KB Output is correct
32 Correct 1 ms 1664 KB Output is correct
33 Correct 1 ms 1664 KB Output is correct
34 Correct 1 ms 1664 KB Output is correct
35 Correct 201 ms 1664 KB Output is correct
36 Correct 8 ms 1664 KB Output is correct
37 Correct 2 ms 1664 KB Output is correct
38 Correct 215 ms 1780 KB Output is correct
39 Correct 2 ms 1664 KB Output is correct
40 Correct 2 ms 1664 KB Output is correct
41 Correct 1 ms 1536 KB Output is correct
42 Incorrect 1 ms 1664 KB 'impossible' claimed, but there is a solution
43 Halted 0 ms 0 KB -

Subtask #4
19.0 / 19.0

# Verdict Execution time Memory Grader output
1 Correct 28 ms 2048 KB Output is correct
2 Correct 2 ms 1536 KB Output is correct
3 Correct 13 ms 1536 KB Output is correct
4 Correct 18 ms 1792 KB Output is correct
5 Correct 36 ms 2048 KB Output is correct
6 Correct 31 ms 1912 KB Output is correct
7 Correct 33 ms 1920 KB Output is correct
8 Correct 2 ms 1536 KB Output is correct
9 Correct 1 ms 1536 KB Output is correct
10 Correct 37 ms 2040 KB Output is correct
11 Correct 27 ms 1912 KB Output is correct
12 Correct 32 ms 1912 KB Output is correct
13 Correct 1 ms 1536 KB Output is correct
14 Correct 1 ms 1536 KB Output is correct
15 Correct 36 ms 2040 KB Output is correct
16 Correct 14 ms 1664 KB Output is correct
17 Correct 36 ms 2040 KB Output is correct
18 Correct 35 ms 2040 KB Output is correct
19 Correct 3 ms 1536 KB Output is correct
20 Correct 39 ms 2040 KB Output is correct

Subtask #5
0 / 26.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 1664 KB Output is correct
2 Correct 1 ms 1664 KB Output is correct
3 Correct 1 ms 1664 KB Output is correct
4 Correct 2 ms 1664 KB Output is correct
5 Correct 1 ms 1664 KB Output is correct
6 Correct 1 ms 1664 KB Output is correct
7 Correct 1 ms 1664 KB Output is correct
8 Correct 2 ms 1664 KB Output is correct
9 Correct 1 ms 1664 KB Output is correct
10 Correct 4 ms 1664 KB Output is correct
11 Correct 2 ms 1664 KB Output is correct
12 Correct 2 ms 1664 KB Output is correct
13 Correct 13 ms 1664 KB Output is correct
14 Correct 1 ms 1664 KB Output is correct
15 Correct 1 ms 1664 KB Output is correct
16 Correct 25 ms 1664 KB Output is correct
17 Correct 4 ms 1664 KB Output is correct
18 Correct 4 ms 1792 KB Output is correct
19 Correct 1 ms 1664 KB Output is correct
20 Correct 1 ms 1664 KB Output is correct
21 Correct 1 ms 1664 KB Output is correct
22 Correct 21 ms 1664 KB Output is correct
23 Correct 1 ms 1664 KB Output is correct
24 Correct 3 ms 1664 KB Output is correct
25 Correct 1 ms 1664 KB Output is correct
26 Correct 1 ms 1664 KB Output is correct
27 Correct 24 ms 1664 KB Output is correct
28 Correct 1 ms 1664 KB Output is correct
29 Correct 2 ms 1664 KB Output is correct
30 Correct 2 ms 1792 KB Output is correct
31 Correct 1 ms 1664 KB Output is correct
32 Correct 1 ms 1664 KB Output is correct
33 Correct 1 ms 1664 KB Output is correct
34 Correct 1 ms 1664 KB Output is correct
35 Correct 201 ms 1664 KB Output is correct
36 Correct 8 ms 1664 KB Output is correct
37 Correct 2 ms 1664 KB Output is correct
38 Correct 215 ms 1780 KB Output is correct
39 Correct 2 ms 1664 KB Output is correct
40 Correct 2 ms 1664 KB Output is correct
41 Correct 1 ms 1536 KB Output is correct
42 Incorrect 1 ms 1664 KB 'impossible' claimed, but there is a solution
43 Halted 0 ms 0 KB -