Longest consecutive subsequence

Given an array of positive integers. Find the length of the longest sub-sequence such that elements in the subsequence are consecutive integers, the consecutive numbers can be in any order.

• Time : O(n)
• Space : O(n)

c++

class Solution {
public:
    // arr[] : the input array
    // N : size of the array arr[]

    //Function to return length of longest subsequence of consecutive integers.
    int findLongestConseqSubseq(int arr[], int N) {
        vector<int> dp(100003, 0);
        int res = 0;
        for(int i = 0; i < N; i++) {
            int n = arr[i] + 1;
            if(dp[n] != 0) continue;
            int left = n - dp[n - 1], right = n + dp[n + 1];
            dp[n] = dp[left] = dp[right] = dp[n - 1] + dp[n + 1] + 1;
            res = max(res, dp[n]);
        }
        return res;
    }
};