113.路径总和-ii-1.cpp

/*
 * @lc app=leetcode.cn id=113 lang=cpp
 *
 * [113] 路径总和 II
 */
// LeetCode 官方方法 2 BFS
// @lc code=start
/**
 * 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>> ret;
    unordered_map<TreeNode *, TreeNode *> parent;

    void getPath(TreeNode *node) {
        vector<int> tmp;
        while (node != nullptr) {
            tmp.emplace_back(node->val);
            node = parent[node];
        }
        reverse(tmp.begin(), tmp.end());
        ret.emplace_back(tmp);
    }

    vector<vector<int>> pathSum(TreeNode *root, int targetSum) {
        if (root == nullptr) {
            return ret;
        }

        queue<TreeNode *> que_node;
        queue<int> que_sum;
        que_node.emplace(root);
        que_sum.emplace(0);

        while (!que_node.empty()) {
            TreeNode *node = que_node.front();
            que_node.pop();
            int rec = que_sum.front() + node->val;
            que_sum.pop();

            if (node->left == nullptr && node->right == nullptr) {
                if (rec == targetSum) {
                    getPath(node);
                }
            } else {
                if (node->left != nullptr) {
                    parent[node->left] = node;
                    que_node.emplace(node->left);
                    que_sum.emplace(rec);
                }
                if (node->right != nullptr) {
                    parent[node->right] = node;
                    que_node.emplace(node->right);
                    que_sum.emplace(rec);
                }
            }
        }

        return ret;
    }
};
// @lc code=end