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 longest continuous increasing subsequence is 1, and there are 5 subsequences' length is 1, so output 5.

Constraints:

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

# @lc code=start
using LeetCode

function find_number_of_LIS(nums::Vector{Int})
    len = length(nums)
    len <= 1 && return len
    dp = fill(1, len)
    cnt = copy(dp)
    for i in 2:len, j in 1:(i - 1)
        nums[i] <= nums[j] && continue
        if dp[i] <= dp[j]
            dp[i] = dp[j] + 1
            cnt[i] = cnt[j]
        elseif dp[i] == dp[j] + 1
            cnt[i] += cnt[j]
        end
    end
    max_len = maximum(dp)
    return sum(c for (idx, c) in enumerate(cnt) if dp[idx] == max_len)
end
# @lc code=end

find_number_of_LIS (generic function with 1 method)

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