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Leetcode673-numberOfLongestIncreasingSubsequence

Description

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

Example

Example 1:

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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:
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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.

Solution

Add one array to record the number of each dp[i]

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class Solution {
public int findNumberOfLIS(int[] nums) {
if (nums == null || nums.length == 0) return 0;
int[] dp = new int[nums.length];
int[] count = new int[nums.length];
for (int i = 0; i < nums.length; i++){
dp[i] = 1;
count[i] = 1;
}
int maxLen = dp[0];
int res = 0;
for (int i = 1; i < nums.length; i++){
for (int j = 0; j < i; j++){
if (nums[j] < nums[i]){
if (dp[i] == dp[j] + 1) count[i] += count[j];
if (dp[i] < dp[j] + 1){
dp[i] = dp[j] + 1;
count[i] = count[j];
}
}
}
maxLen = Math.max(maxLen, dp[i]);
}
for(int i = 0; i < dp.length; i++)
if (dp[i] == maxLen) res += count[i];
return res;
}
}