POJ 1517 u Calculate e

  水题，不多说， 看代码。

</pre><pre code_snippet_id="623538" snippet_file_name="blog_20150319_3_5597849" name="code" class="cpp">#include <stdio.h>#include <string.h>#include <math.h>#include <iostream>#include <algorithm>#define mem(a) memset(a, 0, sizeof(a))using namespace std;double ei(int a){    int i, j = 1;    double res = 0;    for (i = 1;i <= a;i++)    {        j *= i;        res += 1.0 / j;    }    return res + 1; }int main(){int i;    printf("n e\n");    printf("- -----------\n");    printf("0 1\n");    printf("1 2\n");    printf("2 2.5\n");    for (i = 3;i <= 9;i++)    {        printf("%d %.9f\n", i, ei(i));    }    return 0;}