Candy Box (easy version) (Codeforces 1183D)
Tags: Greedy, sortings

This problem is actually a subproblem of problem G from the same contest.There are $$$n$$$ candies in a candy box. The type of the $$$i$$$-th candy is $$$a_i$$$ ($$$1 \le a_i \le n$$$).You have to prepare a gift using some of these candies with the following restriction: the numbers of candies of each type presented in a gift should be all distinct (i. e. for example, a gift having two candies of type $$$1$$$ and two candies of type $$$2$$$ is bad). It is possible that multiple types of candies are completely absent from the gift. It is also possible that not all candies of some types will be taken to a gift.Your task is to find out the maximum possible size of the single gift you can prepare using the candies you have.You have to answer $$$q$$$ independent queries.If you are Python programmer, consider using PyPy instead of Python when you submit your code.

Input: The first line of the input contains one integer $$$q$$$ ($$$1 \le q \le 2 \cdot 10^5$$$) — the number of queries. Each query is represented by two lines.The first line of each query contains one integer $$$n$$$ ($$$1 \le n \le 2 \cdot 10^5$$$) — the number of candies.The second line of each query contains $$$n$$$ integers $$$a_1, a_2, \dots, a_n$$$ ($$$1 \le a_i \le n$$$), where $$$a_i$$$ is the type of the $$$i$$$-th candy in the box.It is guaranteed that the sum of $$$n$$$ over all queries does not exceed $$$2 \cdot 10^5$$$.

Output: For each query print one integer — the maximum possible size of the single gift you can compose using candies you got in this query with the restriction described in the problem statement.

Note: In the first query, you can prepare a gift with two candies of type $$$8$$$ and one candy of type $$$5$$$, totalling to $$$3$$$ candies.Note that this is not the only possible solution — taking two candies of type $$$4$$$ and one candy of type $$$6$$$ is also valid.

Sample Inputs:
3
8
1 4 8 4 5 6 3 8
16
2 1 3 3 4 3 4 4 1 3 2 2 2 4 1 1
9
2 2 4 4 4 7 7 7 7

Sample Outputs:
3
10
9

Solution (Python):
import sys
p = int(input())
lines = sys.stdin.readlines()
res = []
for i in range(p):
    n = int(lines[2 * i])
    bucket = {}
    for i in lines[2 * i + 1].split():
        if not bucket.get(i):
            bucket[i] = 0
        bucket[i] += 1
    values = sorted(list(bucket.values()), reverse=True)
    total = 0
    num = None
    curr = None
    for i in values:
        if i == num:
            curr -= 1
        else:
            num = i
            if curr is not None and i >= curr:
                curr -= 1
            else:
                curr = i
        total += curr
        if curr == 0:
            break
    res.append(str(total))
print('\n'.join(res))

Solution (Python):
import sys
q = int(input())
lines = sys.stdin.readlines()
res = []
for i in range(q):
    n = int(lines[2 * i])
    bucket = {}
    for i in lines[2 * i + 1].split():
        if not bucket.get(i):
            bucket[i] = 0
        bucket[i] += 1
    values = sorted(list(bucket.values()), reverse=True)
    total = 0
    num = None
    curr = None
    for i in values:
        if i == num:
            curr -= 1
        else:
            num = i
            if curr is not None and i >= curr:
                curr -= 1
            else:
                curr = i
        total += curr
        if curr == 0:
            break
    res.append(str(total))
print('\n'.join(res))

Solution (Python):
from sys import stdin
input = lambda : stdin.readline()[:-1]
for _ in range(int(input())):
    n = int(input())
    arr = sorted(list(map(int, input().split())))
    dir = {}
    for i in arr:
        dir[i] = dir.get(i, 0) + 1
    brr = sorted(list(dir.values()), reverse=True)
    ans = brr[0]
    cur = brr[0]
    for i in brr[1:]:
        ans += min(cur - 1, i)
        cur = min(cur - 1, i)
        if cur == 0:
            break
    print(ans)