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=0,t=0,m=0;
    while(cin>>s){
        k=0,t=0,m=0;
        for(int i=0;i<s.length();i++){
            if(s[i]>='0'&&s[i]<='9')
                a[k++]=s[i];
        }
        
        for(int i=k-1;i>=0;i--){
            if(t%3!=0||t==0){
                b[m++]=a[i];
                t++;
            }
            else if(t%3==0&&t!=0){
                b[m++]=',';
                t=0;
                i++;
            }
        }
        for(int i=m-1;i>=0;i--)
            cout<<b[i];
        cout<<endl;
    }
    return 0;
}