/**
 * File: binary_search.dart
 * Created Time: 2023-05-12
 * Author: Jefferson (JeffersonHuang77@gmail.com)
 */

/* Binary search (closed interval on both sides) */
int binarySearch(List<int> nums, int target) {
  // Initialize closed interval [0, n-1], i.e., i, j point to the first and last elements of the array
  int i = 0, j = nums.length - 1;
  // Loop, exit when the search interval is empty (empty when i > j)
  while (i <= j) {
    int m = i + (j - i) ~/ 2; // Calculate the midpoint index m
    if (nums[m] < target) {
      // This means target is in the interval [m+1, j]
      i = m + 1;
    } else if (nums[m] > target) {
      // This means target is in the interval [i, m-1]
      j = m - 1;
    } else {
      // Found the target element, return its index
      return m;
    }
  }
  // Target element not found, return -1
  return -1;
}

/* Binary search (left-closed right-open interval) */
int binarySearchLCRO(List<int> nums, int target) {
  // Initialize left-closed right-open interval [0, n), i.e., i, j point to the first element and last element+1
  int i = 0, j = nums.length;
  // Loop, exit when the search interval is empty (empty when i = j)
  while (i < j) {
    int m = i + (j - i) ~/ 2; // Calculate the midpoint index m
    if (nums[m] < target) {
      // This means target is in the interval [m+1, j)
      i = m + 1;
    } else if (nums[m] > target) {
      // This means target is in the interval [i, m)
      j = m;
    } else {
      // Found the target element, return its index
      return m;
    }
  }
  // Target element not found, return -1
  return -1;
}

/* Driver Code*/
void main() {
  int target = 6;
  final nums = [1, 3, 6, 8, 12, 15, 23, 26, 31, 35];

  /* Binary search (closed interval) */
  int index = binarySearch(nums, target);
  print('Index of target element 6 = $index');

  /* Binary search (left-closed right-open interval) */
  index = binarySearchLCRO(nums, target);
  print('Index of target element 6 = $index');
}