#include <stdio.h>
#include <queue>
#include <algorithm>
#include <vector>
#include <utility>
#include <set>
using namespace std;
template <typename T>
using ve = vector<T>;
template <typename T, int sz>
using ar = array<T, sz>;
int n, m;
char ans[1<<18];
int main() {
scanf("%d%d", &n, &m);
ve<int> col(m);
ve<set<int> > g(m);
ve<ar<int, 2>> a(m);
ve<ve<int>> at(n+1);
int j = 0;
for (auto &[x, y] : a) {
scanf("%d%d", &x, &y), --x, --y;
if (x <= y)
at[x].push_back(j), at[y + 1].push_back(j);
else at[0].push_back(j), at[y + 1].push_back(j),
at[x].push_back(j), at[n].push_back(j);
++j;
}
set<int> walk;
for (int i = 0; i < n; ++i) {
for (auto j : at[i])
if (0 == walk.count(j)) walk.insert(j);
else walk.erase(j);
if (walk.size() == 2) {
g[*walk.begin()].insert(*++walk.begin());
g[*++walk.begin()].insert(*walk.begin());
}
if (walk.size() < 2) exit(0 * puts("impossible"));
}
auto bicolor = [&](int u) {
queue<int> q;
q.emplace(u); col[u] = 1;
while (q.size()) {
int x = q.front();
q.pop();
for (auto v : g[x]) {
if (col[v] == col[x])
exit(0 * puts("impossible"));
if (not col[v]) {
col[v] = col[x] == 1 ? 2 : 1;
q.push(x);
}
}
}
};
for (int i = 0; i < m; ++i) if (g[i].size() and col[i] == 0) bicolor(i);
walk.clear();
ar<int, 3> cnt {};
for (int i = 0; i < n; ++i) {
for (auto j : at[i])
if (0 == walk.count(j)) walk.insert(j), ++cnt[col[j]];
else walk.erase(j), --cnt[col[j]];
if (walk.size() >= 3) {
int x[3] = {*walk.begin(), *++walk.begin(), *++++walk.begin()};
if (cnt[1] and cnt[2]) continue;
if (not cnt[1] and not cnt[2]) {
col[x[0]] = 1;
col[x[1]] = 2;
++cnt[1], ++cnt[2];
} else if (not cnt[1]) {
for (int j : {0, 1, 2}) if (col[x[j]] == 0) {
col[x[j]] = 1;
++cnt[1];
break;
}
} else {
for (int j : {0, 1, 2}) if (col[x[j]] == 0) {
col[x[j]] = 2;
++cnt[2];
break;
}
}
}
if (not cnt[1] or not cnt[2])
exit(0 * puts("impossible"));
}
for (int i = 0; i < m; ++i) putchar(col[i] == 1 ? '1' : '0');
return 0;
}
Compilation message
alternating.cpp: In function 'int main()':
alternating.cpp:20:7: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
20 | scanf("%d%d", &n, &m);
| ~~~~~^~~~~~~~~~~~~~~~
alternating.cpp:28:8: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
28 | scanf("%d%d", &x, &y), --x, --y;
| ~~~~~^~~~~~~~~~~~~~~~
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
0 ms |
348 KB |
Output is correct |
| 2 |
Correct |
0 ms |
424 KB |
Output is correct |
| 3 |
Correct |
1 ms |
348 KB |
Output is correct |
| 4 |
Correct |
0 ms |
348 KB |
Output is correct |
| 5 |
Correct |
0 ms |
348 KB |
Output is correct |
| 6 |
Correct |
0 ms |
348 KB |
Output is correct |
| 7 |
Correct |
0 ms |
348 KB |
Output is correct |
| 8 |
Correct |
0 ms |
348 KB |
Output is correct |
| 9 |
Correct |
0 ms |
348 KB |
Output is correct |
| 10 |
Correct |
0 ms |
348 KB |
Output is correct |
| 11 |
Correct |
0 ms |
348 KB |
Output is correct |
| 12 |
Correct |
0 ms |
348 KB |
Output is correct |
| 13 |
Correct |
0 ms |
600 KB |
Output is correct |
| 14 |
Correct |
0 ms |
348 KB |
Output is correct |
| 15 |
Correct |
0 ms |
348 KB |
Output is correct |
| 16 |
Correct |
0 ms |
348 KB |
Output is correct |
| 17 |
Correct |
0 ms |
344 KB |
Output is correct |
| 18 |
Incorrect |
0 ms |
348 KB |
'impossible' claimed, but there is a solution |
| 19 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
0 ms |
348 KB |
Output is correct |
| 2 |
Correct |
0 ms |
424 KB |
Output is correct |
| 3 |
Correct |
1 ms |
348 KB |
Output is correct |
| 4 |
Correct |
0 ms |
348 KB |
Output is correct |
| 5 |
Correct |
0 ms |
348 KB |
Output is correct |
| 6 |
Correct |
0 ms |
348 KB |
Output is correct |
| 7 |
Correct |
0 ms |
348 KB |
Output is correct |
| 8 |
Correct |
0 ms |
348 KB |
Output is correct |
| 9 |
Correct |
0 ms |
348 KB |
Output is correct |
| 10 |
Correct |
0 ms |
348 KB |
Output is correct |
| 11 |
Correct |
0 ms |
348 KB |
Output is correct |
| 12 |
Correct |
0 ms |
348 KB |
Output is correct |
| 13 |
Correct |
0 ms |
600 KB |
Output is correct |
| 14 |
Correct |
0 ms |
348 KB |
Output is correct |
| 15 |
Correct |
0 ms |
348 KB |
Output is correct |
| 16 |
Correct |
0 ms |
348 KB |
Output is correct |
| 17 |
Correct |
0 ms |
344 KB |
Output is correct |
| 18 |
Incorrect |
0 ms |
348 KB |
'impossible' claimed, but there is a solution |
| 19 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
0 ms |
348 KB |
Output is correct |
| 2 |
Correct |
0 ms |
424 KB |
Output is correct |
| 3 |
Correct |
1 ms |
348 KB |
Output is correct |
| 4 |
Correct |
0 ms |
348 KB |
Output is correct |
| 5 |
Correct |
0 ms |
348 KB |
Output is correct |
| 6 |
Correct |
0 ms |
348 KB |
Output is correct |
| 7 |
Correct |
0 ms |
348 KB |
Output is correct |
| 8 |
Correct |
0 ms |
348 KB |
Output is correct |
| 9 |
Correct |
0 ms |
348 KB |
Output is correct |
| 10 |
Correct |
0 ms |
348 KB |
Output is correct |
| 11 |
Correct |
0 ms |
348 KB |
Output is correct |
| 12 |
Correct |
0 ms |
348 KB |
Output is correct |
| 13 |
Correct |
0 ms |
600 KB |
Output is correct |
| 14 |
Correct |
0 ms |
348 KB |
Output is correct |
| 15 |
Correct |
0 ms |
348 KB |
Output is correct |
| 16 |
Correct |
0 ms |
348 KB |
Output is correct |
| 17 |
Correct |
0 ms |
344 KB |
Output is correct |
| 18 |
Incorrect |
0 ms |
348 KB |
'impossible' claimed, but there is a solution |
| 19 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
57 ms |
14024 KB |
Output is correct |
| 2 |
Correct |
3 ms |
2648 KB |
Output is correct |
| 3 |
Correct |
10 ms |
9304 KB |
Output is correct |
| 4 |
Correct |
41 ms |
11612 KB |
Output is correct |
| 5 |
Incorrect |
39 ms |
18448 KB |
'impossible' claimed, but there is a solution |
| 6 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
0 ms |
348 KB |
Output is correct |
| 2 |
Correct |
0 ms |
424 KB |
Output is correct |
| 3 |
Correct |
1 ms |
348 KB |
Output is correct |
| 4 |
Correct |
0 ms |
348 KB |
Output is correct |
| 5 |
Correct |
0 ms |
348 KB |
Output is correct |
| 6 |
Correct |
0 ms |
348 KB |
Output is correct |
| 7 |
Correct |
0 ms |
348 KB |
Output is correct |
| 8 |
Correct |
0 ms |
348 KB |
Output is correct |
| 9 |
Correct |
0 ms |
348 KB |
Output is correct |
| 10 |
Correct |
0 ms |
348 KB |
Output is correct |
| 11 |
Correct |
0 ms |
348 KB |
Output is correct |
| 12 |
Correct |
0 ms |
348 KB |
Output is correct |
| 13 |
Correct |
0 ms |
600 KB |
Output is correct |
| 14 |
Correct |
0 ms |
348 KB |
Output is correct |
| 15 |
Correct |
0 ms |
348 KB |
Output is correct |
| 16 |
Correct |
0 ms |
348 KB |
Output is correct |
| 17 |
Correct |
0 ms |
344 KB |
Output is correct |
| 18 |
Incorrect |
0 ms |
348 KB |
'impossible' claimed, but there is a solution |
| 19 |
Halted |
0 ms |
0 KB |
- |
