Question

How to round a number to a multiple of 8 in C++

Answer 1

#include <iostream>

// The next highest multiple of eight
unsigned int roundToMultipleOf(unsigned int number, unsigned int roundTo) {
    return (number + (roundTo - 1)) & ~(roundTo - 1);
}
 
int main() {
  std::cout << roundToMultipleOf(9, 8) << "\n";
  std::cout << roundToMultipleOf(19, 8) << "\n";
  std::cout << roundToMultipleOf(71, 8) << "\n";
}
 
 
 
/*
run:
 
16
24
72
 
*/

 

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Answer 2

#include <iostream>
#include <cmath>
 
unsigned int roundToMultipleOf(unsigned int number, unsigned int multipleOf) {
    return multipleOf * floor(number / multipleOf);
}
  
int main() {
  std::cout << roundToMultipleOf(9, 8) << "\n";
  std::cout << roundToMultipleOf(19, 8) << "\n";
  std::cout << roundToMultipleOf(71, 8) << "\n";
}
  
  
  
/*
run:
  
8
16
64
  
*/

 

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