HDU 5430 Reflect

Test instructions: Ask in a circular mirror, emit a light source from any point, the number of cases where the N-times reflect back to the starting point.

Solution: Direct Sticking ...

Find the number of coprime in n+1 and n+1, i.e. Euler function.

Code:

#include <stdio.h> #include <iostream> #include <algorithm> #include <string> #include < string.h> #include <math.h> #include <limits.h> #include <time.h> #include <stdlib.h># include<map> #include <queue> #include <set> #include <stack> #include <vector> #define LL Long longusing namespace Std;int eular (int n) {    int ret = 1;    for (int i = 2; I * I <= n; i++)    {        if (n% i = = 0)        {            n/= i;            RET *= i-1;            while (n% i = = 0)            {                n/= i;                RET *= i;}}    }    if (n > 1)        ret *= n-1;    return ret;} int main () {    int T;    while (~SCANF ("%d", &t))    {        while (t--)        {            int n;            scanf ("%d", &n);            printf ("%d\n", Eular (n + 1));        }    }    return 0;}

　　

HDU 5430 Reflect