#include <bits/stdc++.h>
using namespace std;
#define ll long long
const int maxn5 = 2e5 + 10;
int a[200005], b[200005];
bool av[2][200005];
int n, m;
bool ty[200005];
vector <int> seg[200005], ex;
void kill(){
cout << "impossible\n";
exit(0);
}
void solve(){
for(int i = 0; i < m; i++) seg[a[i]].push_back(i);
int id1 = -1, id2 = -1;
for(int i = 0; i < n; i++){
if(b[id1] < i) id1 = -1;
if(b[id2] < i) id2 = -1;
while(!ex.empty() && b[ex.back()] < i) ex.pop_back();
for(auto u : seg[i]) ex.pb(u);
if(id1 == -1){
if(ex.empty()) kill();
id1 = ex.back();
ty[id1] = true;
ex.pop_back();
}
while(!ex.empty() && b[ex.back()] < i) ex.pop_back();
if(id2 == -1){
if(ex.empty()) kill();
id2 = ex.back();
ex.pop_back();
}
}
for(int i = 0; i < m; i++) cout << ty[i];
cout << '\n';
exit(0);
}
int main(){
ios_base::sync_with_stdio(false); cin.tie(NULL);
cin >> n >> m;
for(int i = 0; i < m; i++){
cin >> a[i] >> b[i];
a[i]--;
b[i]--;
}
if(max(n, m) > 20)
solve();
for(int mask = 1; mask < (1 << m) - 1; mask++){
memset(av, false, sizeof av);
for(int i = 0; i < m; i++){
int x = a[i];
while(true){
av[(mask >> i)&1][x] = true;
if(x == b[i]) break;
x++;
if(x == n) x = 0;
}
}
bool re = true;
for(int i = 0; i < n; i++) if(!av[0][i] || !av[1][i]) re = false;
if(re){
for(int i = 0; i < m; i++) cout << ((mask >> i)&1);
return cout << '\n', 0;
}
}
cout << "impossible\n";
}
Compilation message
alternating.cpp: In function 'void solve()':
alternating.cpp:25:27: error: 'class std::vector<int>' has no member named 'pb'
25 | for(auto u : seg[i]) ex.pb(u);
| ^~
