Number of Longest Increasing Subsequence

Given an unsorted array of integers, find the number of longest increasing subsequence.

Example 1:

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

Example 2:

Input: [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.

Note: Length of the given array will be not exceed 2000 and the answer is guaranteed to be fit in 32-bit signed int.

class Solution {
public:
    int findNumberOfLIS(vector<int>& nums) {
        if (nums.size() == 0) {
            return 0;
        }
        vector<int> dp(nums.size(), 1);
        vector<int> count(nums.size(), 1);
        int max_count = 1;
        for (int i = 1; i < nums.size(); i++) {
            for (int j = 0; j < i; j++) {
                if (nums[i] > nums[j]) {
                    if (dp[i] < dp[j] + 1) {
                        dp[i] = dp[j] + 1;
                        count[i] = count[j];
                    } else if (dp[i] == dp[j] + 1) {
                        count[i] += count[j];
                    }
                }
                max_count = max(max_count, dp[i]);
            }
        }
       
        int ans = 0;
        for (int i = 0; i < dp.size(); i++) {
            if (dp[i] == max_count) {
                ans += count[i];
            }
        }
        return ans;
    }
};