1481. Least Number of Unique Integers after K Removals.md

1481. Least Number of Unique Integers after K Removals

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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

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Solution

• mine

  • Java

    Runtime: 56 ms, faster than 50.00%, Memory Usage: 88.8 MB, less than 50.00% of Java online submissions

    //O(N)time O(N)space
    public int findLeastNumOfUniqueInts(int[] arr, int k) {
        Map<Integer, Integer> map = new HashMap<>();
        //record element count
        int[] res = new int[arr.length + 1];
        for (int a : arr) {
            int t = map.getOrDefault(a, 0);
            if (t != 0) {
                //let count is t down
                res[t]--;
            }
            map.put(a, t + 1);
            //let count is t+1 up
            res[t + 1]++;
        }
        int count = 0;
        for (int i = 1; i < res.length; i++) {
            if (res[i] == 0) {
                continue;
            }
            //res[i] is element count is i;
            //so res[i] * i  is the element count is i
            int c = res[i] * i;
            if (k >= c) {
                k -= c;
            } else {
                //[3,3,3]  2    
                //remove k/i =  2 / 3 = 0 
                count += res[i] - k / i;
                k = 0;
            }
        }
        return count;
    }
    

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