习题3-8 循环小数 UVa202

#include<stdio.h>
#include<string.h>
#include<ctype.h>
#include<math.h>

#define max 7000
int arr[max];

int main()
{
	//freopen("input.txt", "r", stdin);
	//freopen("output.txt", "w", stdout);
	int a, b;
	while (scanf("%d %d", &a, &b) == 2)
	{
		memset(arr, 0, sizeof(arr));
		int x = floor((double)a / b);
		printf("%d/%d = %d.", a, b, x);
		int m = a%b;
		int i, period = 0;
		for (int k = 0; k < 7000; k++)//计算小数点后7000位
		{
			m *= 10;
			arr[k] = m / b;
			m = m%b;
		}
		for (i = 0;; i++)
		{
			int ok1 = 1, ok2, l;
			for (l = 1; l <= b; l++)//枚举周期
			{
				ok2 = 1;
				int len = 7000 - i;
				for (int j = 0; j < len; j++)
				if (arr[j + i] != arr[j % l + i])//判断是不是周期
				{
					ok2 = 0;
					break;
				}
				if (ok2)
				{
					period = l; break;
				}

			}
			if (!period)
				ok1 = 0;
			if (ok1)
			{
				printf("(");
				if (period <= 50)
				for (int j = i; j < i + period; j++)
					printf("%d", arr[j]);
				else
				{
					for (int j = i; j < i + 50; j++)
						printf("%d", arr[j]);
					printf("...");
				}
				printf(")\n");
				printf("   %d = number of digits in repeating cycle\n\n", period);
				break;
			}
			else
				printf("%d", arr[i]);
		}
	}
	return 0;
}