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6. Search Insert Position

easyAsked at Lyft

Find the index where target would be inserted into a sorted array.

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

Problem

Given a sorted array of distinct integers and a target value, return the index if the target is found. If not, return the index where it would be inserted to keep the array sorted.

Constraints

  • 1 <= nums.length <= 10^4
  • -10^4 <= nums[i], target <= 10^4
  • Array sorted strictly ascending

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 left to right until you find a value not less than 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 binary search; return left after the loop.

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:

Lyft-specific tips

Lyft loves seeing the half-open binary search template; they reuse it for fare-bucket lookups and expect candidates to handle the empty insertion at the end cleanly.

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