Path SumII.txt

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

For 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]
]

------------------------------------------------------------------------------------

solution:
// Definition for binary tree
struct TreeNode {
  int val;
	TreeNode *left;
	TreeNode *right;
	TreeNode(int x) : val(x), left(NULL), right(NULL) {}
};

void pathSum_aux(TreeNode *root, int sum, vector<vector<int> > &ret, vector<int> &tmp)
{
	if(root == NULL)
		return;
	tmp.push_back(root->val);
	int leftsum = sum - root->val;
	if(leftsum == 0 && root->left == NULL && root->right == NULL)
	{
		ret.push_back(tmp);
	}
	pathSum_aux(root->left, leftsum, ret, tmp);
	pathSum_aux(root->right, leftsum, ret, tmp);
	tmp.pop_back();
}
vector<vector<int> > pathSum(TreeNode *root, int sum)
{
	vector<vector<int> > ret;
	if(root == NULL)
		return ret;
	vector<int> tmp;
	pathSum_aux(root, sum, ret, tmp);
	return ret;
}