cs11_c++_lab4a

SparseVector.hh

 class SparseVector
 {
 private:
     //结构体不一定会用到，不用初始化
     struct node
     {
         int index;
         int value;
         node *next;

         node(int index, int value, node *next = ) : index(index), value(value), next(next) {}
     };
     //这些才是真正的数据成员，要初始化的
     int size;
     node *start;    

     void clear();
     void copyList(const SparseVector &sv);
     void setNonzeroElem(int index, int value);
     void removeElem(int index);
     void checkListOrder();
 public:
     SparseVector(int size);
     const int getSize()const;

     ~SparseVector();
     SparseVector(const SparseVector &sv);
     SparseVector & operator= (const SparseVector &sv);
     int getElem(int idx);
     void setElem(int index, int value);

 };

SparseVector.cc

 #include "SparseVector.hh"
 #include <cassert>
 #include <iostream>
 using namespace std;
 //单参数构造函数
 SparseVector::SparseVector(int size):size(size)
 {
     start = ;
 }

 const int SparseVector::getSize()const
 {
     return size;
 }
 //成员函数都默认带有this指针，所以默认对调用这个函数的对象进行操作，所以不用再传本对象的地址了。
 void SparseVector::clear()
 {
     node *next;
     node *current;
     current = start;
     while(current != )
     {
         next = current->next;
         delete current;
         current = next;
     }
     start = ;
 }
 //对本对象进行操作，调用成员行数也是默认对本对象进行操作，不用传本对象地址。
 SparseVector::~SparseVector()
 {
     clear();
 }

 void SparseVector::copyList(const SparseVector &sv)
 {
     size = sv.getSize();
     node *current;
     node *otherCurrent =sv.start;
     node *prev = ;

     while(otherCurrent != )
     {
         current = new node(otherCurrent->index, otherCurrent->value);
         if(prev == )
         {
             start = current;
             prev = current;
         }
         prev->next = current;
         prev = current;
         otherCurrent = otherCurrent->next;
     }
 }

 SparseVector::SparseVector(const SparseVector &sv)
 {
     copyList(sv);
 }
 //注意自赋值，并且直接调用私有帮助函数。
 SparseVector & SparseVector:: operator= (const SparseVector &sv)
 {
     if (this == &sv)
     {
         return *this;
     }
     clear();
     copyList(sv);
     return *this;
 }
 //难点
 int SparseVector::getElem(int idx)
 {
     node *current = start;
     while(current !=  && current->index < idx)//过滤，两个条件
     {
         current = current->next;
     }
     if(current == )//注意判断条件先后次序，先排除current为0情况
     {
         return ;
     }
     else if(current->index == idx)//如果先执行这个，则current为0时，会直接产生段错误
     {
         return current->value;
     }
     else
     {
         return ;
     }
 }
 //难点，分种情况讨论：1,初始为空。2,插到最后面。3,插到最前面。4，插到中间。
 void SparseVector::setNonzeroElem(int index, int value)
 {
     assert(value != );
     node *current = start;
     node *prev = ;

     if(start == )//容易遗漏，链表初始为空的情况。（1）
     {
         start = new node(index, value);
     }
     else//除此情况外（2,3,4）
     {
         while(current !=  && current->index < index)//过滤，两个条件，保证current指向应该指的结点，或其之后的结点。prev指向值小于应该的结点。
         {
             prev = current;
             current = current->next;//别忘了自增
         }
     /*2选1
      *     if(current == start)//插到最前面，current所指结点大于等于它
         {
             if(current->index == index)//等于
             {
                 current->value = value;
             }
             else//大于
             {
                 node *other = new node(index, value, start);
                 start = other;
             }
         }
         else if(current == 0)//插到最后面，current所指结点小于它
         {
             node *other = new node(index, value, 0);
             prev->next = other;
         }
         else//插到中间，current所指结点大于等于它
         {
             if(current->index == index)//current所指结点等于它
             {
                 current->value = value;
             }
             else//current所指结点结点大于它
             {
                 node *other = new node(index, value, current);
                 prev->next = other;
             }
         }
 */
         if(current == )//插到最后边
         {
             node *other = new node(index, value);
             prev->next = other;
         }
         else if(current -> index == index)//current所指结点等于它的值
         {
             current->value =value;
         }
         else if(current == start)//在最开始的地方
         {
             node *other = new node(index, value, start);
             start = other;
         }
         else //在中间
         {
             node *other = new node(index, value, current);
             prev->next = other;
         }
     }
 }

 void SparseVector::removeElem(int index)
 {
     node *current = start;
     node *prev = ;
     while(current !=  && current->index < index)//过滤
     {
         prev = current;
         current = current->next;
     }
     if(current->index == index)//如果是这个结点
     {
         if(current == start)//是开始结点
         {
             prev = current;
             current = current->next;
             delete prev;
             start = current;
             return;
         }
         else//是中间结点或者是后边的节点（相同的）
         {
             prev->next = current->next;
             delete current;
             return;
         }
     }
     else
     {
         return;
     }
 }

 void SparseVector::setElem(int index, int value)
 {
     if(value != )
     {
         setNonzeroElem(index, value);
     }
     else
     {
         removeElem(index);
     }
 }

 void SparseVector::checkListOrder()
 {
     node *current = start;
     while(current != )
     {
         cout<<"("<<current->index<<"  |  "<<current->value<<")"<<endl;
         current = current->next;
     }
     return;
 }