题解 | 区间翻转

#include <bits/stdc++.h>
using namespace std;
using ll = long long int;
using ld = long double;
using PII=pair<ll,ll>;
using PIII=pair<int,pair<int,int>>;
const ld ESP = 1e-10;
const ld PI = acosl(-1);
const int N=1e6+10;
const int M=2e5+10;
// const int mod = 1000000007;
const int mod = 998244353;
//随机化
random_device rd;
mt19937 gen(rd());
uniform_int_distribution<> dis(1, 1000000000);

void solve(){
    int n,k;
    cin>>n>>k;
    vector<int> v;
    int L=1,R=1,z=1;
    deque<int> q;
    for(int i=1;i<=k;i++){
        int l,r;
        cin>>l>>r;
        while(R<=r){
            if(z)q.push_back(R);
            else q.push_front(R);
            R++;
        }
        while(L<l){
            if(z){
                v.push_back(q.front());
                q.pop_front();
            }else{
                v.push_back(q.back());
                q.pop_back();
            }
            L++;
        }
        z^=1;
    }
    while(R<=n){
        if(z)q.push_back(R);
        else q.push_front(R);
        R++;
    }
    while(L<=n){
        if(z){
            v.push_back(q.front());
            q.pop_front();
        }else{
            v.push_back(q.back());
            q.pop_back();
        }
        L++;
    }
    for(int i=0;i<v.size();i++){
        cout<<v[i]<<" ";
    }
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int _=1;
    // cin>>_;
    while(_--){
        solve();
    }
    return 0;
}