Leetcode Problem 1995. Count Special Quadruplets

1995. Count Special Quadruplets

Leetcode Solutions

Map-based Approach for Counting Quadruplets

  1. Initialize a counter res to 0 to store the number of quadruplets found.
  2. Create a map count to store the frequency of differences nums[d] - nums[c].
  3. Iterate over the array in reverse order starting from the second to last element, treating it as b.
  4. For each b, iterate over all elements before it, treating them as a, and add to res the frequency of nums[a] + nums[b] found in count.
  5. After processing all a for a given b, iterate over all elements after b, treating them as d, and update the map count with the new differences nums[d] - nums[b].
  6. Return the counter res as the final result.
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Brute Force Approach for Counting Quadruplets

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