View Code of Problem 101

#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;
int main(){
    string s;
    char a[999],b[999];
    int k,t,m;
    while(cin>>s){
        k=0,t=0,m=0;
        memset(a,0,sizeof(a));
        for(int i=0;i<s.length();i++){
            if(s[i]>='0'&&s[i]<='9')
                a[k++]=s[i];
        }
        for(long int i=strlen(a)-1;i>=0;i--){
            if(m%3!=0||m==0){
                b[t++]=a[i];
                m++;
            }
            else if(m%3==0&&m!=0){
                b[t++]=',';
                i++;
                m=0;
            }
        }
        for(int i=t-1;i>=0;i--)
            cout<<b[i];
        cout<<endl;
    }
    return 0;
}