Contains duplicate II

Go

Time complexity: $O(n)$ - n is a length of an array of integers
Auxiliary space: $O(n)$ - constant amount of space

func abs(a int, b int) int {
    if (a - b ) < 0 {
        return b - a
    }
    return a - b
}

func containsNearbyDuplicate(nums []int, k int) bool {
    // key is number, value is it's index in parameter array
    numberIndexMap := make(map[int]int)

    for i :=0 ; i <len(nums); i++ {
        // the same number
        value, isFound := numberIndexMap[nums[i]]
        // distance between the same numbers
        distanceBetween := abs(value, i)

        if (isFound && distanceBetween <= k) {
            return true;
        }

        numberIndexMap[nums[i]] = i
    }

    return false;
}

Typescript

Time complexity: $O(n)$ - n is a length of an array of integers
Auxiliary space: $O(n)$ - constant amount of space

function twoSum(nums: number[], target: number): number[] {
    const numberIndexHash = {};

    return nums.some((num, index) => {
        if(num in numberIndexHash && Math.abs(index - numberIndexHash[num]) <= k) {
            return true;
        }

        numberIndexHash[num] = index;
    })
}

thoughtbook

Contains duplicate II

Go

Typescript