题解 | #不一样的逆序数#

打表题

#include<bits/stdc++.h>
using namespace std;
int a[]={2178,21978,219978,2199978,21782178,21999978};
int n;
int main(){
    cin>>n;
    int cnt=0;
    for (int i=0;i<sizeof(a)/sizeof(a[0]);++i){
        if (n/4>=a[i])cnt++;
        else break;
    }
    cout<<cnt<<endl;
    if (cnt==0)return 0;
    for (int i=0;i<cnt;++i){
        cout<<a[i]<<" "<<a[i]*4<<endl;
    }
    return 0;
}