PhonePe | SDE- 1 | Bangalore

Given an array of integers 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.
Constraint: 0 <= nums.length <= 10^5, 10^9 <= nums[i] <= 10^9, 0 <= k <= 10^5
Example:
nums = [1,2,3,1], k = 3 => true
nums = [1,0,1,1], k = 1 => true

Given an integer array nums and an integer k, return the number of pairs (i, j) where i < j and |nums[i] - nums[j]| == k.
Example:
nums = [1,2,2,1], k = 1 => 2 ([1,2] at (0,1) and (3,2))
nums = [1,3,1,5], k = 2 => 1 ([1,3] at (0,1))

Given a binary string (e.g., '0110100') where '1' means light is present and '0' means no light. Each switch, when turned on at index i, illuminates indices i-1, i, and i+1. Find the minimum number of switches to turn on to illuminate all '0's in the string.