最直接的解法

#include <bits/stdc++.h>
using namespace std;
int main()
{
    int n;
    int m;
    string bb;
    string zh,mbu,dy;
    cin>>n;
    for(int i=0;i<n;i++)
    { cin>>m;
     cin>> zh;
     cin>> dy;
     cin>> bb;
     cin>>mbu;     
     cout<<m<<" "<< zh<<" "<< dy <<" ";
     int b;
     if(zh=="m"&&mbu=="mm")
     {
         b=m*1000;
     }
     if(zh=="km"&&mbu=="m")
     {
         b=m*1000;
     }
     if(zh=="km"&&mbu=="mm")
     {
         b=m*1000*1000;
     }
     if(zh=="g"&&mbu=="mg")
     {
         b=m*1000;
     }
     if(zh=="kg"&&mbu=="g")
     {
         b=m*1000;
     }
     if(zh=="kg"&&mbu=="mg")
     {
         b=m*1000*1000;
     }
     cout<< b <<" "<< mbu<<endl;    
        
    }
    return 0;
}