closest_int_same_weight.cc

#include <stdexcept>

#include "test_framework/generic_test.h"

using std::invalid_argument;

unsigned long long ClosestIntSameBitCount(unsigned long long x) {
  const static int kNumUnsignedBits = 64;
  for (int i = 0; i < kNumUnsignedBits - 1; ++i) {
    if (((x >> i) & 1) != ((x >> (i + 1)) & 1)) {
      x ^= (1UL << i) | (1UL << (i + 1));  // Swaps bit-i and bit-(i + 1).
      return x;
    }
  }

  // Throw error if all bits of x are 0 or 1.
  throw invalid_argument("All bits are 0 or 1");
}

int main(int argc, char* argv[]) {
  std::vector<std::string> args{argv + 1, argv + argc};
  std::vector<std::string> param_names{"x"};
  return GenericTestMain(args, "closest_int_same_weight.cc",
                         "closest_int_same_weight.tsv", &ClosestIntSameBitCount,
                         DefaultComparator{}, param_names);
}