Contains Duplicate II
Given an array and integer k, return True if there are two distinct indices i and j such that nums[i] == nums[j] and abs(i - j) <= k.
Example:
1,2,3,1 3
True
- The input array is
[1, 2, 3, 1]and the integerkis 3. - We iterate through the array to find duplicate elements within a distance of k indices.
- At index 0, the value is 1, and at index 3, the value is also 1, with an index difference of abs(0−3)=3, which satisfies the condition abs(i−j)≤k.
- Since a duplicate is found within the specified distance, the function returns
True.
Constraints:
- 1 <= len(nums) <= 10^5
- -10^9 <= nums[i] <= 10^9
- 0 <= k <= 10^5
Background Knowledge
The problem "Contains Duplicate II" involves using hash maps to keep track of the indices of elements in an array. A hash map is a data structure that stores key-value pairs, allowing for efficient lookups, insertions, and deletions. In this context, we can use a hash map to store the indices of the elements we've seen so far. The problem also involves the concept of sliding windows, where we consider a subset of the array elements within a certain distance k.
The key concept here is to understand how to utilize the hash map to keep track of the indices of the elements and how to apply the sliding window technique to check for duplicates within the given distance k. This problem requires a good understanding of how to iterate through the array, update the hash map, and check for the condition abs(i - j) <= k.
The mathematical concept of absolute difference is also crucial in this problem, as we need to calculate abs(i - j) to determine if the distance between two indices is within the given limit k. This can be calculated using the formula ∣i−j∣=max(i−j,j−i), but most programming languages provide a built-in abs function to calculate the absolute value.
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