LeetCode Daily Problem P3289: The Troublemaker in Number Town

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Timeline

Timeline

2025-10-31

init

Hash Table

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Problem:

P3289 The Troublemaker in Number Town

https://leetcode.cn/problems/the-two-sneaky-numbers-of-digitville/description/?envType=daily-question&envId=2025-10-31

Use hash table to trade space for time

#include <vector>
#include <unordered_map>
using std::vector;
using std::unordered_map;

class Solution {
    public:
	vector<int> getSneakyNumbers(vector<int> &nums)
	{
		unordered_map<int, int> umap;
		vector<int> res;
		int i, n = nums.size();
		for (i = 0; i < n; i++) {
			umap[nums[i]]++;
			if (umap[nums[i]] == 2) {
				res.push_back(nums[i]);
			}
			if (res.size() == 2) {
				break;
			}
		}
		return res;
	}
};

The O(1) space solution for this problem is also interesting

【Bit manipulation】SixO(1)Solutions，Mathematical operations&In-place repositioning&Group XOR

https://leetcode.cn/problems/the-two-sneaky-numbers-of-digitville/solutions/3820301/wei-yun-suan-liu-chong-o1jie-fa-shu-xue-begur/