673. Number of Longest Increasing Subsequence

https://leetcode.com/problems/number-of-longest-increasing-subsequence/discuss/107293/JavaC++-Simple-dp-solution-with-explanation

每次记载最大长度 然后最后遍历 把等于最大长度的index对应的record里记载的个数加起来

 

class Solution {
    public int findNumberOfLIS(int[] nums) {
        if(nums.length == 0) return 0;
        if(nums.length == 1) return 1;
        int[] dp = new int[nums.length];
        int[] record = new int[nums.length];
        dp[0] = 1;
        record[0]++;
        int max = 1;
        int numLen = 0;
        for(int i = 1; i < nums.length; i++){
            dp[i] = 1;
            record[i] = 1;
            for(int j = i-1; j >= 0; j--){
                if(nums[j] < nums[i]){
                    if(dp[i] == dp[j]+1){
                        record[i] += record[j];
                    }else if(dp[j]+1 > dp[i]){
                        record[i] = record[j];
                        dp[i] = dp[j] + 1;
                    }
                }      
            }
            max = Math.max(max, dp[i]);
        }
        int res = 0;
        System.out.println(max);
        for(int i = dp.length-1; i >= 0; i--){
            if(dp[i] == max){
                res += record[i];
            }
        }
        return res;
        
    }
}