gistfile1.cpp

Path Sum I 
bool hasPathSum(TreeNode *root, int sum) {
    return hasPathSumRe(root, 0, sum);
}

bool hasPathSumRe(TreeNode *root, int value, int sum) {
    if(!root) return false;
    if(!root->left && !root->right){
        if((value+root->val) == sum)
            return true;
        else return false;
    }
    else return hasPathSumRe(root->left, root->val + value, sum)||hasPathSumRe(root->right, root->val + value, sum);
}

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

vector<vector<int> > pathSum(TreeNode *root, int sum) {
    vector<vector<int>> res;
    vector<int> onePossibleSol;
    pathSumRe(root, 0, sum, onePossibleSol, res);
    return res;
}

void pathSumRe(TreeNode *root, int value, int sum, vector<int> oneSol, vector<vector<int>> &res) {
    if(!root) return;
    if(!root->left && !root->right){
        if((value+root->val) == sum){
            oneSol.push_back(root->val);
            res.push_back(oneSol);
        }
        else return ;
    }
    oneSol.push_back(root->val);
    pathSumRe(root->left, root->val + value, sum, oneSol, res);
    pathSumRe(root->right, root->val + value, sum, oneSol, res);
}