Contains Duplicate II

Leetcode Problem 219: Contains Duplicate II

Problem Summary

Given an integer array nums and an integer k, return true if there exist two distinct indices i and j such that nums[i] == nums[j] and the absolute difference |i - j| is at most k.

Constraints:

• The array has between 1 and 100,000 elements.
• Each element is a 32-bit signed integer.
• k is a non-negative integer up to 100,000.

Techniques

• Array
• Hash Table
• Sliding Window

Solution

function containsNearbyDuplicate(nums: number[], k: number): boolean {
    let previousNumbersWithIndex = new Map<number, number>()

    for (let i = 0; i < nums.length; i++) { 
        if (previousNumbersWithIndex.has(nums[i]) && Math.abs(i - previousNumbersWithIndex.get(nums[i])!) <= k) {
            return true
        }

        previousNumbersWithIndex.set(nums[i], i)
    }

    return false
};

console.log(containsNearbyDuplicate([1,2,3,1], 3))