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LeetCode 1338: Reduce Array Size to The Half Solution

Master LeetCode problem 1338 (Reduce Array Size to The Half), a medium challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

1338. Reduce Array Size to The Half

Medium
ArrayHash TableGreedySortingHeap (Priority Queue)

Problem Explanation

Explanation:

To solve this problem, we need to find the minimum size of a set of integers such that at least half of the integers in the array can be removed by removing all occurrences of the integers in the set.

  1. Count the frequency of each integer in the array.
  2. Sort the frequencies in descending order.
  3. Iterate through the sorted frequencies and keep track of the total count of removed integers.
  4. Stop when the total count reaches or exceeds half the size of the array.
  5. Return the number of unique integers visited during the iteration.

Time Complexity: O(n log n) where n is the length of the input array. Space Complexity: O(n) where n is the length of the input array.

Solution Code

import java.util.*;

class Solution {
    public int minSetSize(int[] arr) {
        Map<Integer, Integer> freqMap = new HashMap<>();
        for (int num : arr) {
            freqMap.put(num, freqMap.getOrDefault(num, 0) + 1);
        }
        
        List<Integer> frequencies = new ArrayList<>(freqMap.values());
        Collections.sort(frequencies, Collections.reverseOrder());
        
        int n = arr.length;
        int removedCount = 0;
        int setSize = 0;
        
        for (int freq : frequencies) {
            removedCount += freq;
            setSize++;
            if (removedCount >= n / 2) {
                break;
            }
        }
        
        return setSize;
    }
}

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