update

DSBookCode/BookCode/Two/2.18-2.19/2.18-2.19.cpp

@@ -0,0 +1,124 @@
+#include<iostream>
+#include<string>
+#include<fstream>
+using namespace std;
+#define ERROR 0
+
+typedef struct PNode {
+	float coef; //系数
+	int expn; //指数
+	struct PNode *next;
+} PNode, *Polynomial;
+string head_1, head_2;
+int temp;
+char st = 'A';
+
+void CreatPolyn(Polynomial &P, int m) //算法2.18 多项式的创建
+{
+	//输入m项的系数和指数，建立表示一个多项式的有序链表P
+	Polynomial q, pre, s;
+	int i;
+	P = new PNode;
+	P->next = NULL; //先建立一个带头结点的单链表
+	char filename[20] = { 0 };
+	cout << "请输入有关多项式p" << char(st + 32) << "系数和指数的数据文件名称（文件名+“.txt”，如Poly" << st << ".txt）：" << endl;
+	++st;
+	gets(filename);
+	fstream file;
+	file.open(filename);
+	if (!file) {
+		cout << "未找到相关文件，无法打开！" << endl;
+		exit(ERROR);
+	}
+	file >> head_1 >> head_2;
+	while (!file.eof())
+	{
+		s = new PNode; //生成新结点
+		file >> s->coef >> s->expn; //输入元素值
+		pre = P; //pre用于保存q的前驱，初值为头结点
+		q = P->next;
+		while (q && q->expn < s->expn) //通过比较指数找到第一个大于输入项指数的项q
+		{
+			pre = q;
+			q = q->next;
+		} //while
+		s->next = q; //将输入项s插入到q和其前驱结点pre之间
+		pre->next = s;
+	}//for
+	file.close();
+} //CreatPolyn
+
+void AddPolyn(Polynomial &Pa, Polynomial &Pb) //算法2.19 多项式的相加
+{
+	//多项式加法：Pa=Pa+Pb，利用两个多项式的结点构成“和多项式”
+	Polynomial r, p1, p2, p3;
+	float sum;
+	p1 = Pa->next;
+	p2 = Pb->next; //p1和p2初值分别指向Pa和Pb的第一个结点
+	p3 = Pa; //p3指向和多项式的当前结点，初值为Pa
+	while (p1 && p2) //p1和p2均非空
+	{
+		if (p1->expn == p2->expn) //指数相等
+		{
+			sum = p1->coef + p2->coef; //sum保存两项的系数和
+			if (sum != 0) //系数和不为0
+			{
+				p1->coef = sum; //修改Pa当前结点p1的系数值为两项系数的和
+				p3->next = p1;
+				p3 = p1; //将修改后的Pa当前结点p1链在p3之后，p3指向p1
+				p1 = p1->next; //p1指向后一项
+				r = p2;
+				p2 = p2->next;
+				delete r; //删除Pb当前结点r
+			} else //系数和为0
+			{
+				r = p1;
+				p1 = p1->next;
+				delete r; //删除Pb当前结点p1
+				r = p2;
+				p2 = p2->next;
+				delete r; //删除Pb当前结点p2
+			}
+		} else if (p1->expn < p2->expn) //Pa当前结点p1的指数值小
+		{
+			p3->next = p1; //将p1链在p3之后
+			p3 = p1; //p3指向p1
+			p1 = p1->next; //p1指向后一项
+		} else //Pa当前结点p2的指数值小
+		{
+			p3->next = p2; //将p2链在p3之后
+			p3 = p2; //p3指向p2
+			p2 = p2->next; //p2指向后一项
+		}
+	} //while
+	p3->next = p1 ? p1 : p2; //插入非空多项式的剩余段
+	delete Pb; //释放Pb的头结点
+} //AddPolyn
+
+
+int main() {
+	Polynomial Pa, Pb;
+	Polynomial p;
+	int i;
+
+	//创建多项式Pa
+	CreatPolyn(Pa, temp); //调用函数，输入Pa每一项的系数和指数
+
+	//创建多项式Pb
+	CreatPolyn(Pb, temp); //调用函数，输入Pa每一项的系数和指数
+
+	AddPolyn(Pa, Pb);
+	cout << "多项式Pa和Pb相加后的结果是：\n";
+	p = Pa->next;
+	i = 0;
+	while (p) //输出相加后的结果，每一项以x^n表示
+	{
+		if (i)
+			cout << " + ";
+		cout << "(" << p->coef << ") * x^" << p->expn;
+		p = p->next;
+		i = 1;
+	}
+	cout << endl;
+	return 0;
+}