latstats.cc

柯老师网站上找到的

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

#define MINNUM	(-1.0e20)
#define MAXNUM	(+1.0e20)

int main()
{
	double x, mean = 0.0, std_dev = 0.0;
	double min = MAXNUM, max = MINNUM;
	double sum = 0.0, sum_of_squares = 0.0;
	int n;

	for (n = 0; scanf("%lf", &x) != EOF; ++n) {
		/* convert seconds to millisecs */
		x *= 1.0e+3;

		if (x < min) min = x;
		if (x > max) max = x;
		sum += x;
		sum_of_squares += (x * x);
	}

	if (n) {
		mean = sum / (double)n;
		std_dev = sqrt((sum_of_squares - (sum * sum / (double)n)) / ((double)n - 1));
	} else {
		min = 0.0;
		max = 0.0;
	}

	printf("Min     = %7.3lfms\n", min);
	printf("Max     = %7.3lfms\n", max);
	printf("Mean    = %7.3lfms\n", mean);
	printf("Std Dev = %7.3lfms\n", std_dev);
}