查找数组中整数的频率并计算x到n次幂

Question

I am trying to solve two different C problems and would like some help and advice in order to better understand how C works and if I'm on the right track with these.

First problem is: To write a function that counts the number of times the value (x) appears among the first (n) elements of an array and returns that count as the frequency of x in theArray. So, an example would be if the array being passed contained the values {5, 7, 23, 8, 23, 67, 23}. And n was 7 and x was 23, then it would return a value of 3 since 23 occurs 3 times within the first 7 elements of the array.

Here is what I have so far:

#include <stdio.h>
#define SIZE 20 /* just for example - function should work with array of any size */

int frequency (int theArray[], int n, int x) 
{
  int i; 
  int count = 0; 

  for (i = 0; i < n; i++) 
  {     
      if (theArray[i] == x) 
      {
        count = count++;
      } 
  }
return (count); 
}


int main(void) 
{
  /* hard code n and x just as examples */
  int n = 12; /* look through first 12 items of array */
  int x = 5; /* value to find */
  int numberFrequency;
  long int theArray[SIZE] = {5,2,3,4,5,6,1,2,10,5,10,12,6,8,7};

  numberFrequency = frequency (theArray[SIZE], n, x);
  printf ("%i", numberFrequency);

  return 0;
}

Currently I'm getting a run time error message and believe it has something to do with the for loop function.

Second problem is: Write a function that raises an integer to a positive integer power. Have the function return a long int, which represents the results of calculating x to the nth power. Do not use the C pow library function and do not use recursion!

My code so far:

#include <stdio.h>

int x_to_the_n (int x, int n)
{
  int i;
  long int result = 1;

  if (n == 0)
  {
    return(result);
  }
  else 
  {
    for (i = 0; i < n ; ++i)
    {
      /* equation here - How can I make (x*x*x*x*x*x,etc...? */
      result = x*(n*x);
    }
  }

return (result);
}

int main(void) 
{
int x =4;
int n =5;
long int result;

result = x_to_the_n (x, n);

printf ("%i", result);
return 0;
}

I can't use recursion so that is out of the question. So, I thought the next best thing would be a for loop. But I'm a little stuck in how I would go about making a for loop do (x x x*x....) based on value of (n). Any help and advice would be appreciated!

Answer 1

In the first problem you give an element after the array as a parameter to your function.

You define a long int array, and pass it into a function expecting an int array.

long int theArray[SIZE] = {5,2,3,4,5,6,1,2,10,5,10,12,6,8,7};

should be

int theArray[SIZE] = {5,2,3,4,5,6,1,2,10,5,10,12,6,8,7};

Instead of this:

numberFrequency = frequency (theArray[SIZE], n, x);

try this:

numberFrequency = frequency (theArray, n, x);

And replace:

count = count++;

with:

count++;