class Solution { public: vector<vector<int>> threeSum(vector<int>& nums) meaning

Explanation of the C++ Code

The given C++ code defines a class named "Solution" with a public member function "threeSum" that takes a reference to a vector of integers as its input.

1. Class Definition: The "Solution" class is declared with a public access specifier.

2. Member Function "threeSum": This member function is defined to take a vector of integers as input and returns a 2D vector of integers.

3. Function Implementation: The "threeSum" function implementation follows the logic to find all unique triplets in the array which gives the sum of zero.

4. Input Parameter: The "nums" vector represents the input array of integers for which the unique triplets with a sum of zero are to be found.

5. Return Value: The function returns a 2D vector containing all the unique triplets (vector of vectors) with a sum of zero.

The code likely implements the popular "Three Sum" problem, which requires finding all unique triplets in the array that sum up to zero. The code is expected to use a specific algorithm or technique to achieve this.