剑指offer：二叉树中和为某一值得路径

/*
struct TreeNode {
    int val;
    struct TreeNode *left;
    struct TreeNode *right;
    TreeNode(int x) :
            val(x), left(NULL), right(NULL) {
    }
};*/
class Solution {
public:
    vector<vector<int>> res;
    vector<int> path;
    void find(TreeNode* root, int sum){
        if(root == nullptr) return;
        path.push_back(root -> val);
        sum -= root -> val;
        if(sum == 0 && !root -> left && !root->right) res.push_back(path);
        else{
            if(root -> left) find(root -> left, sum);
            if(root -> right) find(root -> right, sum);
        }
        path.pop_back();
    }
    vector<vector<int> > FindPath(TreeNode* root,int expectNumber) {
        find(root, expectNumber);
        return res;
    }
};