README.md

673. Number of Longest Increasing Subsequence

Given an integer array nums, return the number of longest increasing subsequences.

Notice that the sequence has to be strictly increasing.

Example 1:

Input: nums = [1,3,5,4,7]
Output: 2
Explanation: The two longest increasing subsequences are [1, 3, 4, 7] and [1, 3, 5, 7].

Example 2:

Input: nums = [2,2,2,2,2]
Output: 5
Explanation: The length of the longest increasing subsequence is 1, and there are 5 increasing subsequences of length 1, so output 5.

Constraints:

• 1 <= nums.length <= 2000
• -106 <= nums[i] <= 106

Solutions (Python)

1. Solution

class Solution:
    def findNumberOfLIS(self, nums: List[int]) -> int:
        dp = [[[10000001, 0], [-1000001, 1]]]

        for num in nums:
            if dp[-1][-1][0] < num:
                dp.append([[1000001, 0]])

            i = bisect.bisect_left(dp, num, key=lambda x: x[-1][0])
            j = bisect.bisect_left(dp[i - 1][::-1], num, key=lambda x: x[0])
            count = dp[i][-1][1] + dp[i - 1][-1][1] - dp[i - 1][-j - 1][1]
            dp[i].append([num, count])

        return dp[-1][-1][1]