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6. Search Insert Position

easyAsked at GitLab

Find the index where a target should be inserted in a sorted array.

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

Problem

Given a sorted distinct integer array nums and a target, return the index where target is found or where it would be inserted to keep order. Must run in O(log n).

Constraints

  • 1 <= nums.length <= 10^4
  • Distinct values
  • O(log n)

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 lo/hi loop; return lo at end.

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

Tradeoff:

GitLab-specific tips

GitLab interviewers love when you draw the invariant for [lo, hi) on the whiteboard before coding — they grade rigor over speed.

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