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$ curl repovive.com/roadmaps/fundamental-algorithms/binary-search/find-first-and-last-position-implementation

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$ curl repovive.com/roadmaps/fundamental-algorithms/binary-search/find-first-and-last-position-implementation

Repovive

Find First and Last Position - Implementation - Binary Search | Fundamental Algorithms | Repovive

Repovive.

Fundamental Algorithms8 sections · 294 units2h total

Open in Course

Find First and Last Position - Implementation

Here is the implementation:

function searchRange(nums, target):
    left = lowerBound(nums, target)

    if left == nums.length or nums[left] != target:
        return [-1, -1]

    right = lowerBound(nums, target + 1) - 1
    return [left, right]

function lowerBound(nums, target):
    left = 0
    right = nums.length

    while left < right:
        mid = (left + right) / 2
        if nums[mid] < target:
            left = mid + 1
        else:
            right = mid

    return left

Two binary searches: $O(\log n)$ time, $O(1)$ space (excluding input).