HDU1787 GCD Again "Euler function"

Topic Links:

http://acm.hdu.edu.cn/showproblem.php?pid=1787

Main topic:

give you an integer n, the number of integers with a range less than n, and an integer greater than 1 for the greatest common divisor of N.

Ideas:

The typical Euler function is deformed. The Euler function φ (n) is the number of greatest common divisor that is used to find an integer less than n, and N is 1.

So the answer to this question is ans = n-φ (n)-1.

AC Code:

#include <iostream> #include <algorithm> #include <cstdio> #include <cstring>using namespace Std;int Euler (int n) {    int ret = n;    for (int i = 2; i*i <= n; ++i)    {        if (n = = = 0)        {            n/= i;            ret = ret-ret/i;        }        while (n% i = = 0)            n/= i;    }    if (n > 1)        ret = ret-ret/n;    return ret;} int main () {    int n;    while (~SCANF ("%d", &n) && N)    {        printf ("%d\n", N-euler (N)-1);    }    return 0;}

HDU1787 GCD Again "Euler function"