#include <bits/stdc++.h>
using namespace std;
/*
se p dois intervalos [a,b] a cobre b, ent a e b tem que ter tipos diferentes
resposta válida tem que ter alguem que cobre outro
ignorar os cobertos
pensar no círculo
vendo os independentes posso colocar eles de cores diferentes pra aproveitar interseções
parte com eles sozinhos tem que ter intervalos contidos bons
qnt par deles fechou
*/
typedef pair<int, int> pii;
typedef pair<long long, long long> pll;
typedef pair<long double, long double> pdd;
const int MAXN = 1e5+10;
vector<int> f[MAXN][2]; // {start, end} fios
pii cb[MAXN];
bool ty[MAXN];
bool ind[MAXN], iscy[MAXN]; // se é independente, ciclo
int pai[MAXN]; // pros ruins, quem contem ele
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
// cout << fixed << setprecision(7);
int n, m;
cin >> n >> m;
int a, b, cyd=0, cyl=1e9+1;
vector<pair<pii, int>> ord, cy;
for (int i=0;i<m;i++){
cin >> a >> b;
cb[i] = {a,b}, pai[i]=-1;
if(b<a){
if (b==a-1){
a=1,b=n;
cb[i]={a,b};
}else{
cyd = max(cyd, b), cyl = min(cyl, a), iscy[i]=1;
cy.push_back({{a,-b}, i});
f[1][0].push_back(i);
f[b][1].push_back(i);
f[a][0].push_back(i);
continue;
}
}
ord.push_back({{a,-b}, i});
f[a][0].push_back(i);
f[b][1].push_back(i);
}
if (!ord.empty()) sort(ord.begin(), ord.end());
bool ruim = 0;
for (auto &x:ord){
x.first.second = -x.first.second;
if (x.first.second <= cyd) continue;
if (x.first.first >= cyl) break;
cyd = x.first.second, ind[x.second]=1, ruim^=1;
}
if (!ord.empty() && ord[0].first.first == 1 && ord[0].first.second==n) ruim=0; // se tem um cara que cobre todo mundo ou nn tem ciclos
else{ // ver ciclos
sort(cy.begin(), cy.end());
cyd = 0;
for (auto &x:cy){
x.first.second*=-1;
if (x.first.second<=cyd) continue;
cyd=x.first.second, ind[x.second]=1, ruim^=1;
}
}
ord.clear();
cy.clear();
set<int> all, im;
vector<int> bn; // bons (ciclos aparecem só no final)
int lst=0;
map<pii, bool> valid;
for (int i=1;i<=n;i++){
for (auto &u:f[i][0]) if (ind[u]){
if (!iscy[u] || i>=cyl) bn.push_back(u);
im.insert(u);
lst = u;
}
while (!f[i][0].empty()){
int u = f[i][0].back();
f[i][0].pop_back();
if (ind[u]) continue;
all.insert(u);
pai[u] = lst; // se um ruim cobre um trecho sem importantes ent ele deveria ser importante
}
if (im.size()+all.size()<2){
cout << "impossible\n";
return 0;
}
if (im.size()==2){
pii srch = {*im.begin(), *next(im.begin())};
if (!valid.count(srch)) valid[srch] = 1;
if (all.empty()) valid[srch] = 0;
}
while (!f[i][1].empty()){
int u = f[i][1].back();
f[i][1].pop_back();
if (ind[u]) im.erase(u);
else all.erase(u);
}
}
int sz = bn.size();
pii want = {-1,-1};
for (auto &x:valid) if (x.second){
want = x.first;
break;
}
if (want.first==-1){ // pegar não-interseção
lst = bn.back();
for (int i=0;i<sz;i++){
int l = cb[bn[i]].first, r=cb[bn[i]].second;
if (l>cyd && (!iscy[bn[i]] || !iscy[lst])){
want = {bn[i], lst};
// cerr << bn[i] << ' ' << lst << ' ' << " for " << cyd << '\n';
break;
}
lst = bn[i];
if (l<=r) cyd=cb[bn[i]].second;
else cyd=n;
}
}
if (ruim && want.first==-1){ // quantidade é ímpar e não tem uma interseção que é válida nem um cara que cobre todo mundo
cout << "impossible\n";
return 0;
}
// for (auto &x:bn) cerr << x << '\n';
if (!ruim){
ty[bn[0]]=1;
for (int i=1;i<sz;i++) ty[bn[i]] = !ty[bn[i-1]];
}else{
for (int i=0;i<sz;i++){
if (bn[i]==want.first) want.first = m+i;
else if (bn[i]==want.second) want.second=m+i;
}
want.first-=m, want.second-=m;
if (want.second<want.first) swap(want.first, want.second);
bool color = 1;
if (want == ((pii){0,sz-1})){
for (int i=0;i<sz;i++){
ty[bn[i]] = color, color=!color;
}
}else{
for (int i=want.second;i<sz;i++){
ty[bn[i]] = color, color=!color;
}
for (int i=0;i<=want.first;i++){
ty[bn[i]] = color, color=!color;
}
}
}
for (int i=0;i<m;i++){
if (pai[i] == -1) cout << ty[i];
else cout << !ty[pai[i]];
}
cout << '\n';
return 0;
}
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
4 ms |
6224 KB |
Output is correct |
| 2 |
Correct |
3 ms |
6224 KB |
Output is correct |
| 3 |
Incorrect |
3 ms |
6224 KB |
'impossible' claimed, but there is a solution |
| 4 |
Halted |
0 ms |
0 KB |
- |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
4 ms |
6224 KB |
Output is correct |
| 2 |
Correct |
3 ms |
6224 KB |
Output is correct |
| 3 |
Incorrect |
3 ms |
6224 KB |
'impossible' claimed, but there is a solution |
| 4 |
Halted |
0 ms |
0 KB |
- |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
4 ms |
6224 KB |
Output is correct |
| 2 |
Correct |
3 ms |
6224 KB |
Output is correct |
| 3 |
Incorrect |
3 ms |
6224 KB |
'impossible' claimed, but there is a solution |
| 4 |
Halted |
0 ms |
0 KB |
- |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
43 ms |
13296 KB |
Output is correct |
| 2 |
Correct |
3 ms |
6224 KB |
Output is correct |
| 3 |
Correct |
15 ms |
10248 KB |
Output is correct |
| 4 |
Correct |
24 ms |
12552 KB |
Output is correct |
| 5 |
Correct |
57 ms |
13540 KB |
Output is correct |
| 6 |
Correct |
43 ms |
12276 KB |
Output is correct |
| 7 |
Correct |
55 ms |
13052 KB |
Output is correct |
| 8 |
Correct |
6 ms |
6736 KB |
Output is correct |
| 9 |
Correct |
5 ms |
6648 KB |
Output is correct |
| 10 |
Correct |
50 ms |
13708 KB |
Output is correct |
| 11 |
Correct |
40 ms |
13052 KB |
Output is correct |
| 12 |
Correct |
54 ms |
13308 KB |
Output is correct |
| 13 |
Correct |
4 ms |
6224 KB |
Output is correct |
| 14 |
Correct |
3 ms |
6224 KB |
Output is correct |
| 15 |
Correct |
43 ms |
11972 KB |
Output is correct |
| 16 |
Correct |
23 ms |
12808 KB |
Output is correct |
| 17 |
Correct |
79 ms |
13696 KB |
Output is correct |
| 18 |
Correct |
73 ms |
11524 KB |
Output is correct |
| 19 |
Correct |
4 ms |
6736 KB |
Output is correct |
| 20 |
Correct |
35 ms |
11392 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
4 ms |
6224 KB |
Output is correct |
| 2 |
Correct |
3 ms |
6224 KB |
Output is correct |
| 3 |
Incorrect |
3 ms |
6224 KB |
'impossible' claimed, but there is a solution |
| 4 |
Halted |
0 ms |
0 KB |
- |
