Skip to main content

6. Search Insert Position

easyAsked at Quora

Return the index where a target should be inserted to keep a sorted array sorted.

By Alex Chen, Founder, InterviewChamp.AI · Last verified

Problem

Given a sorted array of distinct integers and a target, return the index if the target is found; otherwise return the index where it would be if inserted. You must write an O(log n) algorithm.

Constraints

  • 1 <= nums.length <= 10^4
  • All values are distinct
  • -10^4 <= target, nums[i] <= 10^4

Examples

Example 1

Input
nums = [1,3,5,6], target = 5
Output
2

Example 2

Input
nums = [1,3,5,6], target = 2
Output
1

Approaches

1. Linear scan

Walk until you find the first index >= target.

Time
O(n)
Space
O(1)
for (let i = 0; i < nums.length; i++) if (nums[i] >= target) return i;
return nums.length;

Tradeoff:

2. Binary search

Standard lower_bound: contract is lo as insertion point.

Time
O(log n)
Space
O(1)
function searchInsert(nums, target) {
  let lo = 0, hi = nums.length;
  while (lo < hi) {
    const mid = (lo + hi) >> 1;
    if (nums[mid] < target) lo = mid + 1;
    else hi = mid;
  }
  return lo;
}

Tradeoff:

Quora-specific tips

Quora screens on lower-bound binary search because their ranking service inserts new questions into sorted-by-score buckets and needs the insert index in microseconds.

Solve it now

Free. No sign-up. Python and JavaScript run instantly in your browser.

Output

Press Run or Cmd+Enter to execute

Practice these live with InterviewChamp.AI

Drill Search Insert Position and other Quora interview questions under real-loop conditions with instant feedback on your reasoning, complexity claims, and code.

Practice these live with InterviewChamp.AI →