Top/C++/Strings/Null-terminated/Answer-nullterm-4

Answer to Question nullterm-4

It recomputes strlen(s) each time around the loop. Suppose that s has n characters. Then the loop goes around n times. Each time, it spends time proportional to n to compute strlen(s). So the total amount of time is proportial to n2. (If you buy x things and each one costs y dollars then your total bill is xy dollars.)

You could compute strlen(s) once and save it in a variable. But it is not really necessary to compute strlen(s) even once. A better approach is to end the loop when s[i] is a null character. 

int numNonblanks(const char* s)
{
  int count = 0;

  for(int i = 0; s[i] != '\0'; i++)
  {
    if(s[i] != ' ')
    {
      count++;
    }
  }
  return count;
}