一元多項式加法與乘法
阿新 • • 發佈:2022-03-06
一元多項式的加法與乘法運算
題意理解
設計函式分別求兩個一元多項式的乘積與和
求解思路
- 多項式表示
- 程式框架
- 讀多項式
- 加法實現
- 乘法實現
- 多項式輸出
多項式的表示
僅表示非零項
-
陣列
- 程式設計簡單、除錯容易
- 需要事先確定陣列大小
一種比較好的實現方法是:動態陣列
-
連結串列
- 動態性強
- 程式設計略為複雜、除錯比較困難
資料結構設計
typedef struct PolyNode *Polynomial;
struct PolyNode{
int coef;
int expon;
Polynomial link;
};
程式框架搭建
int main(){ 讀入多項式1 讀入多項式2 乘法運算並輸出 加法運算並輸出 return 0; } int main(){ Polynomial P1, P2, PP, PS; P1 = ReadPoly(); P2 = ReadPoly(); PP = Mult(P1, P2); PrintPoly(PP); PS = Add(P1, P2); PrintPoly(PS); }
需要設計的函式:
- 讀取一個多項式
- 兩多項式相乘
- 兩多項式相加
- 多項式輸出
如果讀入多項式
Polynomial ReadPoly(){ Polynomial P, Rear, t; int c, e, N; scanf("%d", &N); P = (Polynomial)malloc(sizeof(struct PolyNode));//連結串列頭空結點 P->link = NULL; Rear = P; while (N--){ scanf("%d%d",&c, &e); Attach(c, e, &Rear);//將當前項插入多項式尾部 } t = P; P = P->link; free(t);//刪除臨時生成的頭結點 return P; }
Rear初值是多少?
兩種處理方法:
-
Rear初值為NULL
在Attach函式中根據Rear是否為NULL做不同處理
-
Rear指向一個空姐點
void Attach(int c, int e, Polynomial *pRear){
Polynomial P;
P = (Polynomial)malloc(sizeof(struct PolyNode));
P->coef = c;//對新結點賦值
P->expon = e;
P->link = P;
*pRear = P;//修改*pRear值
}
如何將兩個多項式相加
Polynomial Add(Polynomial P1, Polynomial P2){
t1 = P1;
t2 = P2;
P = (Polynomial)malloc(sizeof(struct PolyNode));
Rear = P;
while (t1 && t2){
if (t1->expon == t2->expon){
}
else if (t1->expon > t2->expon){
}
else{
}
while (t1){
}
while (t2){
}
}
return P;
}
如何將兩個多項式相乘
方法:
- 將乘法運算轉換為加法運算
將P1當前項(ci,ei)乘P2多項式,再加到結果多項式裡
t1 = P1;
t2 = P2;
P = (Polynomial)malloc(sizeof(struct PolyNode));
Rear = P;
while (t2){
Attach(t1->coef * t2->coef, t1->expon + t2->expon, &Rear);
t2 = t2->link;
}
- 逐項插入
將P1當前項(c1i, e1i)乘P2當前項(c2i, e2i),並插入到結果中。並插入到結果中。關鍵是要找到插入位置
初始結果多項式可由P1第一項乘P2獲得
Polynomial Mult(Polynomial P1, Polynomial P2){
Polynomial P, Rear, t1, t2, t;
int c, e;
if (!P1||!P2) return NULL;
t1 = P1;
t2 = P2;
while(t2){//先用P1的第1項乘以P2,得到P
Attach(t1->coef * t2->coef, t1->expon + t2->expon, &Rear);
t2 = t2->link;
}
t1 = t1->link;
while (t1){
t2 = P2;
Rear = P;
while (t2){
e = t1->expon + t2->expon;
c = t1->coef * t2->coef;
while (Rear->link && Rear->link->expon > e)
Rear = Rear->link;
if (Rear->link && Rear->link->expon == e){
if (Rear->link->coef + c)
Rear->link->coef+=c;
else{
t = Rear->link;
Rear->link = t->link;
free(t);
}
}
else{
t = (Polynomial)malloc(sizeof(struct PolyNode));
t->coef = c;
t->expon = e;
t->link = Rear->link;
Rear->link = t;
Rear = Rear->link;
}
t2 = t2->link;
}
t1 = t1->link;
}
t2 = P;P = P->link; free(t2);
}
如何將多項式輸出
void PrintPoly(Polynomial P){
//輸出多項式
int flat = 0;
if(!P){
printf("0 0\n");return;
}
while(P){
if(!flag)
flag = 1;
else
printf(" ");
}
printf("\n");
}