"945. Minimum Increment to Make Array Unique" is a medium-level problem and is featured as the problem of the day for June 14, 2024, on LeetCode. The solution provided in the accompanying video is implemented in Java, but the approach is explained using a dry-run on a whiteboard, making it accessible and beneficial for people with different programming backgrounds.
The problem requires finding the minimum number of increments needed to make all elements in an array unique. The brute force approach involves sorting the array and then checking each element to see if it is less than or equal to the previous element. The equality check ensures that the current number doesn't repeat by being equal to the previous element, and the lesser check ensures that no same elements are present before the current element. If the current element is not greater than the previous element, it is incremented to be one more than the previous element, and the number of increments needed is counted. The total number of moves required to make the array unique is the sum of all these increments.
This approach works but can be time-consuming for large arrays. A more efficient approach leverages counting sort, particularly useful given the problem constraints. In this method, a frequency array of length 100001 (based on the given constraints) is created to store the frequency of each element in the original array. This frequency array is populated such that the index represents the element value, and the value at that index represents its frequency in the original array. Then, the frequency array is used to make necessary increments to ensure all elements are unique, counting the moves required. The last index (`100000`) is handled by calculating the sequential sum from 1 to `n` where `n` is the excess frequency, ensuring the final set of elements are unique.
This counting sort approach optimizes the process by efficiently handling increments and minimizing the total number of moves needed. To understand the optimized approach fully, watch the video till the end.
Link to the problem: leetcode.com/p...
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11 сен 2024
