Package g2501_2600.s2552_count_increasing_quadruplets

Class Solution

java.lang.Object
g2501_2600.s2552_count_increasing_quadruplets.Solution
public class Solution extends java.lang.Object
2552 - Count Increasing Quadruplets.

Hard

Given a 0-indexed integer array nums of size n containing all numbers from 1 to n, return the number of increasing quadruplets.

A quadruplet (i, j, k, l) is increasing if:

  • 0 <= i < j < k < l < n, and
  • nums[i] < nums[k] < nums[j] < nums[l].

Example 1:

Input: nums = [1,3,2,4,5]

Output: 2

Explanation:

  • When i = 0, j = 1, k = 2, and l = 3, nums[i] < nums[k] < nums[j] < nums[l].

  • When i = 0, j = 1, k = 2, and l = 4, nums[i] < nums[k] < nums[j] < nums[l]. There are no other quadruplets, so we return 2.

Example 2:

Input: nums = [1,2,3,4]

Output: 0

Explanation:

There exists only one quadruplet with i = 0, j = 1, k = 2, l = 3, but since nums[j] < nums[k], we return 0.

Constraints:

  • 4 <= nums.length <= 4000
  • 1 <= nums[i] <= nums.length
  • All the integers of nums are unique. nums is a permutation.

  • Constructor Summary

    Constructors
    Constructor
    Description
    Solution()
     

  • Method Summary

    Modifier and Type
    Method
    Description
    long
    countQuadruplets(int[] nums)
     

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Constructor Details

    • Solution

      public Solution()

  • Method Details

    • countQuadruplets

      public long countQuadruplets(int[] nums)