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Overview

Searches sorted data by comparing with the middle element and reducing the search range each step.
TimeSpace
O(log(n))O(1)
Binary Search only works when the data is sorted.

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Implementation

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Iterative

Iterative Binary Search
function binarySearch(arr, target) {
  let left = 0;
  let right = arr.length - 1;

  while (left <= right) {
    const mid = Math.floor((left + right) / 2);

    if (arr[mid] < target) {
      left = mid + 1;
    } else if (arr[mid] > target) {
      right = mid - 1;
    } else {
      return mid;
    }
  }

  return false;
}

console.log(binarySearch([-6, -2, 0, 2, 3, 3, 5, 7, 12], 5)); // 6

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Recursive

Recursive Binary Search
function binarySearch(arr, target, left = 0, right = arr.length - 1) {
  if (left > right) {
    return false;
  }

  const mid = Math.floor((left + right) / 2);

  if (arr[mid] < target) {
    return binarySearch(arr, target, mid + 1, right);
  } else if (arr[mid] > target) {
    return binarySearch(arr, target, left, mid - 1);
  } else {
    return mid;
  }
}

console.log(binarySearch([-6, -2, 0, 2, 3, 3, 5, 7, 12], 5)); // 6

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