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6. Search Insert Position

easyAsked at Riot Games

Find where to insert a value in a sorted array — Riot uses this for binary-search fluency before MMR bucket lookup questions.

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

Problem

Given a sorted distinct integer array and a target value, return the index if found. Otherwise return the index where it would be inserted to keep the array sorted.

Constraints

  • 1 <= nums.length <= 10^4
  • -10^4 <= nums[i] <= 10^4
  • nums distinct and sorted

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 forward and return 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 lower bound

Halve the range until lo == hi.

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:

Riot Games-specific tips

Riot uses lower-bound binary search to slot a player into the right Elo/Glicko MMR bucket without re-sorting the bucket list each tick.

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Output

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