Implement binary search on sorted arrays for O(log n) performance. Master the two-pointer technique and understand when linear search is needed.

• Binary search on sorted arrays for O(log n) performance

function binarySearch(arr, target) {
  let left = 0, right = arr.length - 1;
  while (left <= right) {
    const mid = Math.floor((left + right) / 2);
    if (arr[mid] === target) return mid;
    if (arr[mid] < target) left = mid + 1;
// ...

• Binary search finds target
• Binary search returns -1 for missing

• Array must be sorted for binary search; O(log n) vs O(n)
• Two-pointer: one at start, one at end; move based on condition
• Watch off-by-one errors: left <= right, not left < right

Implement binary search on sorted arrays for O(log n) performance. Master the two-pointer technique and understand when linear search is needed.

• Binary search on sorted arrays for O(log n) performance

function binarySearch(arr, target) {
  let left = 0, right = arr.length - 1;
  while (left <= right) {
    const mid = Math.floor((left + right) / 2);
    if (arr[mid] === target) return mid;
    if (arr[mid] < target) left = mid + 1;
// ...

• Binary search finds target
• Binary search returns -1 for missing

• Array must be sorted for binary search; O(log n) vs O(n)
• Two-pointer: one at start, one at end; move based on condition
• Watch off-by-one errors: left <= right, not left < right