2554. Maximum Number of Integers to Choose From a Range I

#Problem

You are given an integer array banned and two integers n and maxSum. You are choosing some number of integers following the below rules:

• The chosen integers have to be in the range [1, n].
• Each integer can be chosen at most once.
• The chosen integers should not be in the array banned.
• The sum of the chosen integers should not exceed maxSum.

Return the maximum number of integers you can choose following the mentioned rules.

https://leetcode.com/problems/maximum-number-of-integers-to-choose-from-a-range-i/

Example 1:

Input: banned = [1,6,5], n = 5, maxSum = 6
Output: 2
Explanation: You can choose the integers 2 and 4.
2 and 4 are from the range [1, 5], both did not appear in banned, and their sum is 6, which did not exceed maxSum.

Example 2:

Input: banned = [1,2,3,4,5,6,7], n = 8, maxSum = 1
Output: 0
Explanation: You cannot choose any integer while following the mentioned conditions.

Example 3:

Input: banned = [11], n = 7, maxSum = 50
Output: 7
Explanation: You can choose the integers 1, 2, 3, 4, 5, 6, and 7.
They are from the range [1, 7], all did not appear in banned, and their sum is 28, which did not exceed maxSum.

Constraints:

• 1 <= banned.length <= 10⁴
• 1 <= banned[i], n <= 10⁴
• 1 <= maxSum <= 10⁹

#Test Cases

class Solution:
    def maxCount(self, banned: List[int], n: int, maxSum: int) -> int:

import pytest

from solution import Solution


@pytest.mark.parametrize('banned, n, maxSum, expected', [
    ([1,6,5], 5, 6, 2),
    ([1,2,3,4,5,6,7], 8, 1, 0),
    ([11], 7, 50, 7),
])
class Test:
    def test_solution(self, banned, n, maxSum, expected):
        sol = Solution()
        assert sol.maxCount(banned, n, maxSum) == expected

#Thoughts

直接把 banned 里的数字都加到哈希表中，然后从 1 遍历到 n 并跳过 banned 中的值，累加，直到总和超过 maxSum 为止。

#Code

class Solution:
    def maxCount(self, banned: list[int], n: int, maxSum: int) -> int:
        skips = set(banned) # or: set(v for v in banned if 1 <= v <= n), but slower
        cnt = 0
        for v in range(1, n + 1):
            if v in skips: continue
            maxSum -= v
            if maxSum < 0: break
            cnt += 1

        return cnt