View Code of Problem 101

#include<stdio.h>
#include<string.h>
int main() {
	int k,i,count=0;
	char str1[1000],str2[1000];
	while (scanf("%s",str1)!=EOF) {
		k = 0;
		count = 0;
		for (i = strlen(str1)-1; i >= 0; i--) {
			
			if (str1[i] >= '0' && str1[i] <= '9') {
				count++;
				if (count == 3) {
                                  if(i!=0){
                                  	str2[k++] = str1[i];
					str2[k++] = ',';
					count = 0;
                                  }
			          else{
                                  	str2[k++] = str1[i];
                                    count = 0;
                                  }	
					

				}
				else {
					str2[k++] = str1[i];
				}
			}
		}
		str2[k] = '\0';
		for (i = strlen(str2) - 1; i >= 0; i--) {
			printf("%c", str2[i]);
		}
		printf("\n");
	}
	return 0;
}