View Code of Problem 101

#include<stdio.h>
int main()
{
	char str[100], str1[100] = { 0 };
	int len, i, flag, j;
	while (scanf("%s",&str)!=EOF)
	{
		len = strlen(str);
		flag = 3;
		j=0;
		for (i = len - 1; i >= 0; i--)
		{
			if (str[i] != ',')
			{
				str1[j++] = str[i];
				flag--;
				if (flag == 0 && i != 0)
				{
					str1[j++] = ',';
					flag = 3;
				}
			}
		}
		for (i = j - 1; i >= 0; i--)
		{
			printf("%c", str1[i]);
		}
		printf("\n");
	}
	return 0;
}