Package g3201_3300.s3251_find_the_count_of_monotonic_pairs_ii

Class Solution

java.lang.Object
g3201_3300.s3251_find_the_count_of_monotonic_pairs_ii.Solution
public class Solution extends Object
3251 - Find the Count of Monotonic Pairs II.

Hard

You are given an array of positive integers nums of length n.

We call a pair of non-negative integer arrays (arr1, arr2) monotonic if:

  • The lengths of both arrays are n.
  • arr1 is monotonically non-decreasing , in other words, arr1[0] <= arr1[1] <= ... <= arr1[n - 1].
  • arr2 is monotonically non-increasing , in other words, arr2[0] >= arr2[1] >= ... >= arr2[n - 1].
  • arr1[i] + arr2[i] == nums[i] for all 0 <= i <= n - 1.

Return the count of monotonic pairs.

Since the answer may be very large, return it modulo 109 + 7.

Example 1:

Input: nums = [2,3,2]

Output: 4

Explanation:

The good pairs are:

  1. ([0, 1, 1], [2, 2, 1])
  2. ([0, 1, 2], [2, 2, 0])
  3. ([0, 2, 2], [2, 1, 0])
  4. ([1, 2, 2], [1, 1, 0])

Example 2:

Input: nums = [5,5,5,5]

Output: 126

Constraints:

  • 1 <= n == nums.length <= 2000
  • 1 <= nums[i] <= 1000

  • Constructor Details

    • Solution

      public Solution()

  • Method Details

    • countOfPairs

      public int countOfPairs(int[] nums)