Solution.cpp

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
using pii = pair<int, int>;

class Solution {
public:
    map<int, vector<pii>> d;

    vector<vector<int>> verticalOrder(TreeNode* root) {
        dfs(root, 0, 0);
        vector<vector<int>> ans;
        for (auto& [_, v] : d) {
            sort(v.begin(), v.end(), [&](pii& a, pii& b) {
                return a.first < b.first;
            });
            vector<int> t;
            for (auto& x : v) {
                t.push_back(x.second);
            }
            ans.push_back(t);
        }
        return ans;
    }

    void dfs(TreeNode* root, int depth, int offset) {
        if (!root) return;
        d[offset].push_back({depth, root->val});
        dfs(root->left, depth + 1, offset - 1);
        dfs(root->right, depth + 1, offset + 1);
    }
};