Bottom View of Binary Tree

Given a binary tree, print the bottom view from left to right.
A node is included in bottom view if it can be seen when we look at the tree from bottom.

• Time : O(n)
• Space : O(n)

class Solution {
    unordered_map<int, pair<int,int>> mp;
    int mi = 0;
    void helper(Node* root, int dep, int w) {
        if(!root) return;
        mi = min(w, mi);
        if(mp[w].first <= dep) mp[w] = {dep, root->data};
        helper(root->left, dep + 1, w - 1);
        helper(root->right, dep + 1, w + 1);
    }
  public:
    vector <int> bottomView(Node *root) {
        helper(root, 1, 0);
        vector<int> res;
        while(mp.count(mi)) {
            res.push_back(mp[mi].second);
            mi++;
        }
        
        return res;
    }
};