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Update modular_exponentiation.cpp

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Shri Prakash Bajpai 2020-10-22 01:05:42 +05:30 committed by GitHub
parent af3fadc800
commit 365e9a823a
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1 changed files with 10 additions and 10 deletions
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math/modular_exponentiation.cpp
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@ -30,9 +30,10 @@ namespace math {
* @param c integer modulo * @param c integer modulo
* @return a raised to power b modulo c * @return a raised to power b modulo c
*/ */
int power(int a, unsigned int b, int c)
uint64_t power(uint64_t a, uint64_t b, uint64_t c)
{ {
int ans = 1; /// Initialize the answer to be returned uint64_t ans = 1; /// Initialize the answer to be returned
a = a % c; /// Update a if it is more than or a = a % c; /// Update a if it is more than or
/// equal to c /// equal to c
@ -41,7 +42,7 @@ int power(int a, unsigned int b, int c)
{ {
return 0; /// In case a is divisible by c; return 0; /// In case a is divisible by c;
} }
while (b > 0) while (b > 0)
{ {
/// If b is odd, multiply a with answer /// If b is odd, multiply a with answer
@ -49,12 +50,12 @@ int power(int a, unsigned int b, int c)
{ {
ans = (ans*a) % c; ans = (ans*a) % c;
} }
/// b must be even now /// b must be even now
b = b>>1; // b = b/2 b = b>>1; // b = b/2
a = (a*a) % c; a = (a*a) % c;
} }
return ans; return ans;
} }
} // namespace math } // namespace math
@ -66,10 +67,10 @@ int power(int a, unsigned int b, int c)
int main() int main()
{ {
/// Give two numbers num1, num2 and modulo m /// Give two numbers num1, num2 and modulo m
int num1 = 2; uint64_t num1 = 2;
int num2 = 5; uint64_t num2 = 5;
int m = 13; uint64_t m = 13;
std::cout << "The value of "<<num1<<" raised to exponent "<<num2<< std::cout << "The value of "<<num1<<" raised to exponent "<<num2<<
" under modulo "<<m<<" is " << math::power(num1, num2, m); " under modulo "<<m<<" is " << math::power(num1, num2, m);
/// std::cout << "The value of "<<num1<<" raised to exponent "<<num2<<" /// std::cout << "The value of "<<num1<<" raised to exponent "<<num2<<"
@ -77,4 +78,3 @@ int main()
return 0; return 0;
} }