【LeetCode】求二叉树中所有路径和等于给定值的路径：Path Sum II

Given a binary tree and a sum, find all root-to-leaf paths where each path's sum equals the given sum.

Note: A leaf is a node with no children.

Example:

Given the below binary tree and sum = 22,

      5
     / \
    4   8
   /   / \
  11  13  4
 /  \    / \
7    2  5   1

Return:

[
   [5,4,11,2],
   [5,8,4,5]
]

代码如下：

class Solution {
public:
    vector<vector<int>> pathSum(TreeNode* root, int sum) {
        vector<vector<int> > result;
        vector<int> cur;
        
        pathSum(root, sum, cur, result);
        return result;
    }
    
    void pathSum(TreeNode* root, int gap, vector<int>& cur, vector<vector<int> > &result) {
        if(!root) return;
        
        cur.push_back(root->val);
        // 遇到叶子结点进行计算，看是否满足要求，满足要求直接保存
        if(!root->left && !root->right && root->val == gap) {
            result.push_back(cur); // 这个地方不能直接返回，
        }
        
        pathSum(root->left, gap - root->val, cur, result);
        pathSum(root->right, gap - root->val, cur, result);
        
        cur.pop_back(); //  把当前元素弹出来，继续后边的递归遍历
    }
};