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6. Search Insert Position

easyAsked at DigitalOcean

Find the index of a target in a sorted array or the insertion point — DigitalOcean uses this to confirm binary-search fluency that supports region-level CIDR-block lookups.

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. If not, return the index where it would be inserted in order.

Constraints

  • 1 <= nums.length <= 10^4
  • Sorted distinct integers
  • -10^4 <= target <= 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 left to right until you find target or a larger value.

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

Maintain [lo, hi]; return lo when loop ends, which is the 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:

DigitalOcean-specific tips

DigitalOcean prizes a clean binary-search invariant because their network-routing layer does CIDR-range lookups on every packet egressing a droplet.

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Output

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