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6. Search Insert Position

easyAsked at Wise

Find the index where a target should be inserted to keep an array sorted — Wise uses this to test if you can insert a new FX quote into a sorted price ladder.

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 if inserted in order. You must write an O(log n) algorithm.

Constraints

  • 1 <= nums.length <= 10^4
  • nums has no duplicates

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 hit 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

Standard lower-bound binary search. End pointer is the answer.

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:

Wise-specific tips

Wise interviewers will ask what happens if the price ladder is full of duplicates — be ready to discuss lower-bound vs upper-bound semantics in a peer-matching FX book.

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Output

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