Example 1:

Input: nums1 = [1,1,3,2], nums2 = [2,3], nums3 = [3]
Output: [3,2]
Explanation: The values that are present in at least two arrays are:
- 3, in all three arrays.
- 2, in nums1 and nums2.

Example 2:

Input: nums1 = [3,1], nums2 = [2,3], nums3 = [1,2]
Output: [2,3,1]
Explanation: The values that are present in at least two arrays are:
- 2, in nums2 and nums3.
- 3, in nums1 and nums2.
- 1, in nums1 and nums3.

Example 3:

Input: nums1 = [1,2,2], nums2 = [4,3,3], nums3 = [5]
Output: []
Explanation: No value is present in at least two arrays.

Constraints:

• 1 <= nums1.length, nums2.length, nums3.length <= 100
• 1 <= nums1[i], nums2[j], nums3[k] <= 100

Solution: Hashmap / Bitmask

s[x] := bitmask of x in all array[i]

s[x] = 101 => x in array0 and array2

Time complexity: O(n1 + n2 + n3)
Space complexity: O(n1 + n2 + n3)

// Author: Huahua
class Solution {
public:
  vector<int> twoOutOfThree(vector<int>& nums1, vector<int>& nums2, vector<int>& nums3) {
    unordered_map<int, int> s;    
    for (int x : nums1) s[x] |= 1;
    for (int x : nums2) s[x] |= 2;
    for (int x : nums3) s[x] |= 4;
    vector<int> ans;
    for (auto [x, v] : s)
      if (__builtin_popcount(v) >= 2) ans.push_back(x);
    return ans;
  }
};

The post 花花酱 LeetCode 2032. Two Out of Three appeared first on Huahua's Tech Road.

For example,
Given [100, 4, 200, 1, 3, 2],
The longest consecutive elements sequence is [1, 2, 3, 4]. Return its length: 4.

Your algorithm should run in O(n) complexity.

class Solution {
public:
    int longestConsecutive(vector<int> &num) {
        unordered_map<int,int> m;
        int ans = 0;
        for(auto n : num) {
            if(m.count(n)) continue;
            if(m.count(n-1) && m.count(n+1)){
                int l = m[n-1], r = m[n+1];
                m[n] = m[n-l] = m[n+r] = r+l+1;
            } else if(m.count(n-1)) {
                int l = m[n-1];
                m[n] = m[n-l] = l+1; 
            } else if(m.count(n+1)) {
                int r = m[n+1];
                m[n] = m[n+r] = r+1;
            } else {
                m[n] = 1;
            }
            ans = max(ans, m[n]);
        }
        return ans;
    }
};

The post 花花酱 LeetCode 128. Longest Consecutive Sequence appeared first on Huahua's Tech Road.