vector<double> x;

size_t i = 0, j = 0;

double tmp = 0.0;

for(i = 0; i < x.size() - 1; ++i)
  for(j = 0; j < x.size() - 1; ++j)
    if(x[j] > x[j+1]) {
      tmp = x[j];
      x[j] = x[j+1];
      x[j+1] = tmp;
    }