Longest_Consecutive_Subsequence

class Solution {
public:

    int bfs (int st, unordered_map<int,int>& num, unordered_map<int,bool>& vis) {
        queue<int> q;
        q.push(st);
        int cmp = 0;
        vis[st] = 1;
        while (!q.empty()) {
            int cur = q.front();
            q.pop();
            cmp++;
            if (num.find(cur+1) != num.end() && vis.find(cur+1) == vis.end()) {
                q.push(cur+1), vis[cur+1] = 1;
            }
            if (num.find(cur-1) != num.end() && vis.find(cur-1) == vis.end()) {
                q.push(cur-1), vis[cur-1] = 1;
            }
        }

        return cmp;

    }
    int longestConsecutive(vector<int>& nums) {

        unordered_map<int,int> num;
        unordered_map<int,bool> vis;
        int ans = 0;

        for (int i=0; i<nums.size(); i++) num[nums[i]] = 1;


        for (auto node : num)
            if (vis.find(node.first) == vis.end())
                ans = max(ans,bfs(node.first,num,vis));


        return ans;
    }
};