题解 | 区间翻转

#include <bits/stdc++.h>
#define int long long
using namespace std;
#define endl '\n'
void work()
{
  int n , k ; cin >> n >> k ; 
  deque<int>dq;
  int f = 1 ; 
  int ad = 1 ; 
  vector<int>res(n + 1);
  bool rev = false ;
  while(k--)
  {
    int l , r ; cin >> l >> r; 
    while(ad <= r)
    {
      if(!rev)
      {
        dq.push_back(ad);
      }
      else
      {
        dq.push_front(ad);
      }
      ad++;
    }


    while(f < l)
    {
      if(!rev)
      {
        res[f] = dq.front();
        dq.pop_front();
      }
      else
      {
        res[f] = dq.back();
        dq.pop_back();
      }
      f++;
    }
    rev = !rev ; 
  }


  while(f <= ad)
{
  if(!rev)
  {
    res[f] = dq.front();
    dq.pop_front();
  }
  else
  {
    res[f] = dq.back();
    dq.pop_back();
  }
  f++;
}
while(ad <= n)
{
  res[ad] = ad ; 
  ad++;
}

for(int i = 1 ; i <= n ; i++)
{
  cout << res[i] << " " ; 
}

}

signed main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    int t = 1 ; 
    while(t--)
    {
        work();
    }
    return 0 ; 
}