Hdoj 1395 2^x mod n = 1 "Violence"

Source: Internet
Author: User

Strategy: observed that 1 or can be divisible by 2 of the number will not be equal to 1, just need to infer is not except 1 odd, in turn find 2^x (mod (n))?

= 1 will be able to

The difficulty: Assume that each time it is based on the original X2 and then the inference will time out. At this point, we can use the congruence theorem.

AC by SWS;

Topic Link: http://acm.hdu.edu.cn/showproblem.php?



#include <stdio.h>int main () {int n;while (scanf ("%d", &n) = = 1) {if (n ==1| | n%2==0) {printf ("2^? MoD%d = 1\n ", n); continue;} Else{int sum = 2, I, DC = 1;for (i = 1;; i + +) if (sum%n! = 1) {sum = sum%n*2;//congruence theorem sumx2%n = = (sum%n) x (2%n) = = (2<n) = > Sum%n*2}elsebreak;printf ("2^%d mod%d = 1\n", I, N);}} return 0;}

Hdoj 1395 2^x mod n = 1 "Violence"

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