binary-search-the-vise.ts

/**
 * Classic Binary Search (Model: "The Vise")
 * * Time Complexity: O(log n)
 * Space Complexity: O(1)
 */
export function binarySearch(nums: number[], target: number): number {
  let left = 0;
  let right = nums.length - 1;

  while (left <= right) {
    // Prevent Integer Overflow: L + (R - L) / 2
    // In JS/TS this isn't critical (Numbers are float64), but for C++/Java/Rust this is standard practice.
    const mid = left + Math.floor((right - left) / 2);

    if (nums[mid] === target) {
      return mid;
    }

    if (nums[mid] < target) {
      // mid is too small (trash).
      // Move the left jaw PAST the trash.
      left = mid + 1;
    } else {
      // mid is too big (trash).
      // Move the right jaw BEFORE the trash.
      right = mid - 1;
    }
  }

  return -1;
}