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Formatted question description: https://leetcode.ca/all/2441.html

2441. Largest Positive Integer That Exists With Its Negative

  • Difficulty: Easy.
  • Related Topics: .
  • Similar Questions: .

Problem

Given an integer array nums that does not contain any zeros, find the largest positive integer k such that -k also exists in the array.

Return the positive integer k. If there is no such integer, return -1.

  Example 1:

Input: nums = [-1,2,-3,3]
Output: 3
Explanation: 3 is the only valid k we can find in the array.

Example 2:

Input: nums = [-1,10,6,7,-7,1]
Output: 7
Explanation: Both 1 and 7 have their corresponding negative values in the array. 7 has a larger value.

Example 3:

Input: nums = [-10,8,6,7,-2,-3]
Output: -1
Explanation: There is no a single valid k, we return -1.

Constraints:

  • 1 <= nums.length <= 1000
  • -1000 <= nums[i] <= 1000
  • nums[i] != 0

Solution (Java, C++, Python)

  • class Solution {
    public int findMaxK(int[] nums) {
        int ans = -1;
        Set<Integer> s = new HashSet<>();
        for (int v : nums) {
            s.add(v);
        }
        for (int v : s) {
            if (s.contains(-v)) {
                ans = Math.max(ans, v);
            }
        }
        return ans;
    }
}

  • class Solution {
public:
    int findMaxK(vector<int>& nums) {
        unordered_set<int> s(nums.begin(), nums.end());
        int ans = -1;
        for (int& v : nums) {
            if (s.count(-v)) {
                ans = max(ans, v);
            }
        }
        return ans;
    }
};

  • class Solution:
    def findMaxK(self, nums: List[int]) -> int:
        ans = -1
        s = set(nums)
        for v in s:
            if -v in s:
                ans = max(ans, v)
        return ans


  • func findMaxK(nums []int) int {
	s := map[int]bool{}
	for _, v := range nums {
		s[v] = true
	}
	ans := -1
	for v := range s {
		if s[-v] && ans < v {
			ans = v
		}
	}
	return ans
}

  • function findMaxK(nums: number[]): number {
    const set = new Set(nums);
    let res = -1;
    for (const num of set) {
        if (set.has(-num)) {
            res = Math.max(num, res);
        }
    }
    return res;
}


  • use std::collections::HashSet;
impl Solution {
    pub fn find_max_k(nums: Vec<i32>) -> i32 {
        let set = nums.into_iter().collect::<HashSet<i32>>();
        let mut res = -1;
        for &num in set.iter() {
            if set.contains(&(-num)) {
                res = res.max(num);
            }
        }
        res
    }
}

Explain:

nope.

Complexity:

  • Time complexity : O(n).
  • Space complexity : O(n).

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