计数排序

class Solution {
    public int[] getLeastNumbers(int[] arr, int k) {
        if(k == 0 || arr.length == 0) return new int[0];
        int[] count = new int[10001];
        for(int num : arr) count[num]++;
        
        int[] result = new int[k];
        int index = 0;
        for(int i = 0; i < count.length; i++){
            while(count[i]-- > 0 && index < k) result[index++] = i;
            if(index == k) break;
        }
        return result;
    }
}