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c++cmath

What is the time complexity of log10 function in cmath?

What is the time complexity of log10 function in cmath ? Its nowhere mentioned on the internet. Does anyone know for sure ?

Later edit: My initial question was if the following code is faster.

int numOfDigits(int n) {
  return (int)log10(n) + 1;
}

than this 

int numOfDigits(int n) {
  int count = 0;
  while(n) {
    count ++;
    n /= 10;
  }
  return 0;
}

i know for sure that the second function time complexity is O(log(n)). What's the time complexity of the first function.

Solution

  • The standard does not specify complexity requirement for the log10 function.

    However, I would expect a reasonable implementation to have constant complexity.