为什么我的电源 function 在这里不能正常工作？

Question

I've tried changing variable types but this is still not working.

double power(double a, long long b){

    while(b>1){
        a *= a;
        b--;
    }

return a;
}

Answer 1

Your code won't run properly when b>2 because when you're doing a = a*a;the second time it won't be a^3 but a^4 and the next time it will be a^8 and so on. The right code would be something like this below:

double power(double a, long long b){

double k = 1;
    while(b>0){
        k *= a;
        b--;
    }

return k;
}

Answer 2

You're changing a on every iteration. Say you call it like power(2, 3) .

First you do 2 * 2 and assign this to a . Next iteration, you'll do again a * a which is 4 * 4 . Just keep the result in a variable and don't change the arguments:

double power(double a, long long b){
    double r = a;
    while(b>1){
        r *= a;
        b--;
    }

    return r;
}

Answer 3

you are changing the variable a and it courses the defects. what you can do instead is

double power(double base, double exp)
{
  double result = 1;
  for(int i = 0; i < exp; i++)
  {
    result *= base;
  }
  return result;
}