peak finding

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

#define LEN 10

int find_peak(int *arr, size_t length);

int main(void) {
  int arr[LEN];

  srand(time(NULL));
  for (size_t i = 0; i < LEN; i++) {
    arr[i] = rand() % 16 + 1;
  }

  printf("[ ");
  for (size_t i = 0; i < LEN; i++) {
    printf("%d ", arr[i]);
  }
  printf("]\n");

  printf("Found peak: %d", find_peak(arr, LEN));
  return 0;
}

int find_peak(int *arr, size_t length) {
  size_t i = 0, j = length - 1;

  while (i < j) {
    size_t mid = i + (j - i) / 2;

    if (arr[mid] >= arr[mid + 1] && arr[mid] >= arr[mid - 1])
      return arr[mid];

    if (arr[mid] <= arr[mid + 1])
      i = mid;
    else
      j = mid;
  }
}