USACO:Preface Numbering

/*ID: Jang LawrencePROG: prefaceLANG: C++*/#include<iostream>#include<cstring>#include<cstdio>#include<algorithm>#include<queue>#define mp make_pairusing namespace std;int n;char s[][10][5]={{"M","MM","MMM"},{"C","CC","CCC","CD","D","DC","DCC","DCCC","CM"},{"X","XX","XXX","XL","L","LX","LXX","LXXX","XC"},{"I","II","III","IV","V","VI","VII","VIII","IX"}};char str[]={"IVXLCDM"};int num[10],id[26];void count(int x){    int cnt=3;    while(x)    {        int k=x%10;        x/=10;        if(k==0) ;        else        {            for(int i=0;s[cnt][k-1][i]!='\0';++i)            num[id[s[cnt][k-1][i]-'A']]++;        }        cnt--;    }}int main(){  #ifndef  DEBUG  freopen("preface.in","r",stdin);  freopen("preface.out","w",stdout);  #endif  for(int i=0;str[i]!='\0';++i)  id[str[i]-'A']=i;  scanf("%d",&n);  for(int i=1;i<=n;++i)  count(i);  for(int i=0;i<7;++i)  if(num[i]!=0)  printf("%c %d\n",str[i],num[i]);    return 0;}