1481. Least Number of Unique Integers after K Removals

Posted 2020-12-11 wentiliangkaihua

Given an array of integers arr and an integer k. Find the least number of unique integers after removing exactly k elements.

 

Example 1:

Input: arr = [5,5,4], k = 1
Output: 1
Explanation: Remove the single 4, only 5 is left.

Example 2:

Input: arr = [4,3,1,1,3,3,2], k = 3
Output: 2
Explanation: Remove 4, 2 and either one of the two 1s or three 3s. 1 and 3 will be left.

 

Constraints:

• 1 <= arr.length <= 10^5
• 1 <= arr[i] <= 10^9
• 0 <= k <= arr.length

class Solution {
   public int findLeastNumOfUniqueInts(int[] arr, int k) {
        Map<Integer, Integer> map = new HashMap<>();
        for (int n : arr) map.put(n, map.getOrDefault(n, 0) + 1);
        List<Integer> l = new ArrayList<>(map.keySet());
        Collections.sort(l, (a, b) -> map.get(a) - map.get(b));
        int n = map.size(), remove = 0, idx = 0;
        while (k > 0 && idx < n) {
            k -= map.get(l.get(idx++));
            if (k >= 0) remove++;
        }
        return n - remove;
    }
}

这就是差距吧。。