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) {}
 * };
 */
class Solution {
public:
    vector<vector<int>> verticalTraversal(TreeNode* root) {
        vector<tuple<int, int, int>> nodes;
        function<void(TreeNode*, int, int)> dfs = [&](TreeNode* root, int i, int j) {
            if (!root) {
                return;
            }
            nodes.emplace_back(j, i, root->val);
            dfs(root->left, i + 1, j - 1);
            dfs(root->right, i + 1, j + 1);
        };
        dfs(root, 0, 0);
        sort(nodes.begin(), nodes.end());
        vector<vector<int>> ans;
        int prev = -2000;
        for (auto [j, _, val] : nodes) {
            if (j != prev) {
                prev = j;
                ans.emplace_back();
            }
            ans.back().push_back(val);
        }
        return ans;
    }
};