1481

1481. Least Number of Unique Integers after K Removals (Medium)

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

Related Topics:
Array, Sort

Solution 1.

// OJ: https://leetcode.com/problems/least-number-of-unique-integers-after-k-removals/
// Author: github.com/lzl124631x
// Time: O(N + UlogU) where U is the number of unique counts
// Space: O(N)
class Solution {
public:
    int findLeastNumOfUniqueInts(vector<int>& A, int k) {
        unordered_map<int, int> cnt;
        for (int n : A) cnt[n]++;
        map<int, int> m;
        for (auto &p : cnt) m[p.second]++;
        int ans = cnt.size();
        for (auto &p : m) {
            int n = min(p.second, k / p.first);
            if (n == 0) break;
            ans -= n;
            k -= p.first * n;
        }
        return ans;
    }
};