4.在二元树中找出和为某一值的所有路径

///////////////////////////////////////////////////////////////////////
// Find paths whose sum equal to expected sum
///////////////////////////////////////////////////////////////////////
void FindPath
    (
    BinaryTreeNode*   pTreeNode,    // a node of binary tree
    int               expectedSum,  // the expected sum
    std::vector<int>& path,         // a path from root to current node
    int&              currentSum    // the sum of path
    )
{
    if(!pTreeNode)
        return;

    currentSum += pTreeNode->m_nValue;
    path.push_back(pTreeNode->m_nValue);

    // if the node is a leaf, and the sum is same as pre-defined, 
    // the path is what we want. print the path
    bool isLeaf = (!pTreeNode->m_pLeft && !pTreeNode->m_pRight);
    if(currentSum == expectedSum && isLeaf)
    {    
        std::vector<int>::iterator iter = path.begin();
        for(; iter != path.end(); ++ iter)
            std::cout << *iter << ‘\t‘;
        std::cout << std::endl;
    }

    // if the node is not a leaf, goto its children
    if(pTreeNode->m_pLeft)
        FindPath(pTreeNode->m_pLeft, expectedSum, path, currentSum);
    if(pTreeNode->m_pRight)
        FindPath(pTreeNode->m_pRight, expectedSum, path, currentSum);

    // when we finish visiting a node and return to its parent node,
    // we should delete this node from the path and 
    // minus the node‘s value from the current sum
    currentSum -= pTreeNode->m_nValue;
    path.pop_back();
} 

void FindPath(
    BinaryTreeNode*   pTreeNode,    // a node of binary tree
    int               expectedSum  // the expected sum
    )
{
    int curSum = 0;
    std::vector<int> path;
    FindPath(pTreeNode,expectedSum,path,curSum);
}