BinarySearch.c

#include <stdio.h>

int BinarySearch(int array[], int size, int value) {
  int start = 0;
  int end = size - 1;
  int middle = end / 2;

  while (start < end && array[middle] != value) {
    // new start
    if (value > array[middle])
      start = middle + 1;

    // new end
    if (value < array[middle])
      end = middle - 1;

    // new middle
    middle = (start + end) / 2;
  }

  if (array[middle] == value)
    return middle;

  return -1;
}

int main() {
  int value;
  int array[] = {1, 5, 10, 12, 18, 22, 87, 90, 112, 129};
  size_t size = sizeof(array) / sizeof(array[0]);

  printf("Please provide the number you want to value for: ");
  scanf("%d", &value);

  int pos = BinarySearch(array, size, value);

  if (pos != -1)
    printf("Found in position = %d.\nValue = %d\n", pos, array[pos]);
  else
    printf("Not found\n");

  return 0;
}