两种文件输入输出

利用文件输入和输出的好处:不必每次测试都要手工输入,避免输出太多而无法看清
准备:现在debug下面建立两个文件:input.txt(保存输入数据的文件) output.txt(输入数据的文件)
1.输入输出重定向
例子:

#include <stdio.h>
#include <time.h>
#define MOD 100000
#define LOCAL
int main()
{
#ifdef LOCAL
	//文件输入输出重定向,解决多次输入问题
	freopen("input.txt", "r", stdin);
	freopen("output.txt", "w", stdout);
#endif
	int n, i, factorial = 1, s = 0, j;
	scanf("%d", &n);
	for(i = 1; i < n; i++)
	{
		factorial = 1;
		for(j = 1; j <= i; j++)
		{
			factorial = factorial * j % MOD;
		}
		s = (s + factorial) % MOD;
	}
	printf("%d\n", s );
	printf("Time Used = %.2lf\n", (double)clock() / CLOCKS_PER_SEC);
	return 0;
}

第二种:利用文件打开的和关闭,非重定向

#include <stdio.h>
#include <time.h>
#define MOD 100000
int main()
{
	FILE *fin, *fout;
	fin = fopen("input.txt", "rb");
	fout = fopen("output.txt", "wb");
	int n, i, factorial = 1, s = 0, j;
	fscanf(fin ,"%d", &n);
	for(i = 1; i < n; i++)
	{
		factorial = 1;
		for(j = 1; j <= i; j++)
		{
			factorial = factorial * j % MOD;
		}
		s = (s + factorial) % MOD;
	}
	fprintf(fout,"%d\n", s );
	fprintf(fout, "Time Used = %.2lf\n", (double)clock() / CLOCKS_PER_SEC);
	fclose(fin);
	fclose(fout);
	return 0;
}