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6. Search Insert Position

easyAsked at Canva

Find where to insert a value in a sorted array — Canva tests this to see if you reach for binary search on ordered z-index lists.

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

Problem

Given a sorted array of distinct integers and a target value, return the index where target is found. If not, return the index where it would be inserted in order, with O(log n) runtime.

Constraints

  • 1 <= nums.length <= 10^4
  • nums sorted ascending
  • -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 a value >= 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

Use lo/hi pointers; collapse the range; return lo as the insertion index. Classic O(log n) search.

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:

Canva-specific tips

Canva interviewers want a tight binary search with correct half-open invariants, since the editor's z-index ladder uses similar insertion logic.

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Output

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