Zhe Jiang University

Design

Target: Find the sum and the product of 2 polynomials.

Data Structure
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typedef struct PolyNode *Polynomial;
struct PolyNode{
  int coef; 
  int expon; 
  Polynomial link;
};
Structure of the program
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Polynomial P1, P2, PP, PS;

P1 = ReadPoly();
P2 = ReadPoly();
PP = Multi(P1, P2);
PrintPoly(PP);
PS = Add(P1, P2);
PrintPoly(PS);

Some New Ideas

  1. If you want to pass in a variable and let the function change it, you have to pass in a more ‘fundamental’ thing - that is - a pointer to this variable. If passing the value itself, there will be a ‘shell’ to preent it from being changed.

  2. (linked list) Getting the node just before the target node can be sometimes more flexible. It is easier to delete a node.

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    t = Rear->link;
    Rear->link = t->link;
    free(t);

  3. Creating a linked list: in writing a connecting function, in order to avoid if-clauses to find whether it is the first node of a list, you can just create am empty node at the head of a linked list and in the end delete it.

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    P->link = NULL; 
    Rear = P; 
    while(N--){
      scanf("%d %d", &c, &e); 
      Attach(c, e, &Rear); 
    }

  4. The usage of scanf is easier than expected. The computer will stop getting input every time it meets a space or an enter. The way to get input can simply be like the example below.

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    scanf("%d", &N); 
    P = (Polynomial)malloc(sizeof(struct PolyNode)); 
    P->link = NULL; 
    Rear = P; 
    while(N--){
      scanf("%d %d", &c, &e); 
      Attach(c, e, &Rear); 
    }

    REMARK: The pause enter or space will be dumped by the computer instead of being inputed.