0219-contains-duplicate-ii

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Description

Given an integer array nums and an integer k, return true if there are two distinct indices i and j in the array such that nums[i] == nums[j] and abs(i - j) <= k.

 

Example 1:

Input: nums = [1,2,3,1], k = 3
Output: true

Example 2:

Input: nums = [1,0,1,1], k = 1
Output: true

Example 3:

Input: nums = [1,2,3,1,2,3], k = 2
Output: false

 

Constraints:

  • 1 <= nums.length <= 105
  • -109 <= nums[i] <= 109
  • 0 <= k <= 105

Solution(Python)

class Solution:
    def containsNearbyDuplicate(self, nums: List[int], k: int) -> bool:
        #  0 .. n- 1
        # abs(i-j) <= k
        # 
        # valid nums[i] == nums[j] and abs(i-j) <= k
        # 
        # invalid nums[i] != nums[j] 
        # 
        # if abs(i-j) <= k true
        # 
        # l =0 
        # r = 0
        # r -> n-1
        #   nums[l] != nums[r]  loop  l +=1
        #   if abs(i-j) <= k return True
        #   
        hashset = {}
        for i,num in enumerate(nums):
            if num in hashset and abs(i - hashset[num]) <= k:
                return True
            hashset[num] = i
        return False

Dry Run