作为成员的指针函数错误

我正在尝试创建以下成员函数，但我得到了以下错误：

class ListStudentGradeDB
{
private:

public:
    struct node 
    {
        std::string studentName;
        int studentScore;
        node *next;
    };
    // line below is to create shortcut to node* nodePtr.
    typedef struct node* nodePtr;
    nodePtr head;
    nodePtr curr;
    nodePtr temp;

    // Constructor
    ListStudentGradeDB();

    // member functions for merge sort
    void MergeSort();
    nodePtr msort(nodePtr start, int size);
    nodePtr merge(nodePtr list1, nodePtr list2, int size1, int size2);
    // Destructor
    ~ListStudentGradeDB(void);

};

    //ListStudentGradeDB.cpp 
    nodePtr ListStudentGradeDB::msort(node* start, int size)
    {
        if(size > 1)
        {
            int midSize = size/2;
            int count = midSize;
            node* mid = start;
            while(count)
        {
            mid = mid->next;
            count--; 
        }
        return merge(msort(start, midSize), msort(mid, size - midSize), midSize, size - midSize);
    }
    else
        return start;
}   

nodePtr ListStudentGradeDB::merge(nodePtr list1, nodePtr list2, int size1, int size2)
{
    // Trivial cases
    if(size1 == 0)
        return list2;
    if(size2 == 0)
        return list1;
    // Choose the bigger element from the front of the two lists
    // and put it at the head of the new list and call merge 
    // again with the sub lists
    if (list1->studentScore < list2->studentScore || list1->studentScore == list2->studentScore)
    {
        list1->next = merge(list1->next, list2, size1-1, size2);
        return list1;
    }
    else
    {
        list2->next = merge(list1, list2->next, size1, size2-1);
        return list2;
    }
}

错误

>1>c:\users\vypham\documents\visualstudio>2012\projects\cmpe_180\cmp180_final\liststudentgradedb.cpp（534）：错误>C2143:语法错误：缺少"；"在"ListStudentGradeDB:：msort"之前>1>c:\users\vypham\documents\visualstudio>2012\projects\cmpe_180\cmp180_final\liststudentgradedb.cpp（534）：错误>C4430:缺少类型说明符-假定为int。注意：C++没有>支持默认的int 1>c:\users\vypham\documents\visualstudio>2012\projects\cmpe_180\cmp180_final\liststudentgradedb.cpp（535）：错误>C4430:缺少类型说明符-假定为int。注意：C++没有>支持默认的int 1>c:\users\vypham\documents\visualstudio>2012\projects\cmpe_180\cmp180_final\liststudentgradedb.cpp（535）：错误>C2556:"int ListStudentGradeDB:：msort（ListStudentGradeDB:，node*，int）">：重载函数与的不同之处仅在于返回类型>'ListStudentGradeDB:：nodePtr>ListStudentGradeDB:：msort（ListStudentGradeDB:：nodePtr，int）'1>>c:\users\vypham\documents\visualstudio>2012\projects\cmpe_180\cmp180_final\liststudentgradedb.h（88）：请参阅>"ListStudentGradeDB:：msort"的声明>1>c:\users\vypham\documents\visualstudio>2012\projects\cmpe_180\cmp180_final\liststudentgradedb.cpp（535）：错误>C2040:"ListStudentGradeDB:：msort"："int（ListStudentGradeDB:节点>*，int）'在间接级别上与'ListStudentGradeDB:：nodePtr（ListStudentGradeDB:；nodePtr，int）]不同>1>c:\users\vypham\documents\visualstudio>2012\projects\cmpe_180\cmp180_final\liststudentgradedb.cpp（546）：错误>C2264:"ListStudentGradeDB:：msort"：函数定义或>申报；函数未调用1>c:\users\vypham\documents\visual>工作室>2012\projects\cmpe_180\cmp180_final\liststudentgradedb.cpp（553）：错误>C2143:语法错误：缺少"；"在"ListStudentGradeDB:：merge"之前>1>c:\users\vypham\documents\visualstudio>2012\projects\cmpe_180\cmp180_final\liststudentgradedb.cpp（553）：错误>C4430:缺少类型说明符-假定为int。注意：C++没有>支持默认的int 1>c:\users\vypham\documents\visualstudio>2012\projects\cmpe_180\cmp180_final\liststudentgradedb.cpp（553）：错误>C2086:"int nodePtr"：重新定义1>>c:\users\vypham\documents\visualstudio>2012\projects\cmpe_180\cmp180_final\liststudentgradedb.cpp（534）：请参阅>"nodePtr"1>的声明c:\users\vypham\documents\visual studio>2012\projects\cmpe_180\cmp180_final\liststudentgradedb.cpp（554）：错误>C4430:缺少类型说明符-假定为int。注意：C++没有>支持默认的int 1>c:\users\vypham\documents\visualstudio>2012\projects\cmpe_180\cmp180_final\liststudentgradedb.cpp（554）：错误>C2556:'int>ListStudentGradeDB:：merge>：重载函数与的不同之处仅在于返回类型>'ListStudentGradeDB:：nodePtr>ListStudentGradeDB:：merge>1>c:\users\vypham\documents\visualstudio>2012\projects\cmpe_180\cmp180_final\liststudentgradedb.h（89）：请参阅>"ListStudentGradeDB:：merge"的声明>1>c:\users\vypham\documents\visualstudio>2012\projects\cmpe_180\cmp180_final\liststudentgradedb.cpp（554）：错误>C2040:"ListStudentGradeDB:：merge"："int>（ListStudentGradeDB:：nodePtr，ListStudentGradeDB:：nodePtr，int，int）'>间接级别与'ListStudentGradeDB:：nodePtr不同>（ListStudentGradeDB:：nodePtr，ListStudentGradeDB:：nodePtr，int，int）'>1>c:\users\vypham\documents\visualstudio>2012\projects\cmpe_180\cmp180_final\liststudentgradedb.cpp（568）：错误>C2264:"ListStudentGradeDB:：merge"：函数定义错误或>申报；函数未调用1>c:\users\vypham\documents\visual>工作室>2012\projects\cmpe_180\cmp180_final\liststudentgradedb.cpp（573）：错误>C2264:'ListStudentGradeDB:：merge'

我正在尝试为两个成员函数返回指针。有人能帮忙吗？