endl超时

2023牛客寒假练习5-E

#include<iostream>
#include<algorithm>
#include<numeric>
#include<vector>

using namespace std;

typedef pair<int,int> pii;
int main()
{
    std::ios::sync_with_stdio(false);
    cin.tie(0),cout.tie(0);
    int n;
    cin>>n;
    
    vector<int> a(n+1);
    iota(a.begin(),a.end(),0);
    
    vector<vector<pii>> ans;
    
    while(!is_sorted(a.begin()+1,a.end(),greater<int>()))
    {
        vector<pii> tmp;
        for(int i=2;i<=n;i++)
        {
            if(a[i]>a[i-1])
            {
                swap(a[i],a[i-1]);
                tmp.push_back({a[i],a[i-1]});
                i++;
            }
        }
        ans.push_back(tmp);
    }
    
    cout<<ans.size()<<endl;
    
    for(auto a:ans)
    {
        cout<<a.size()<<endl;
        for(auto [x,y]:a)
        {
            cout<<x<<' '<<y<<endl;
        }
    }
    
}