一元多项式的表示及相加 【链表的应用】

#include <iostream>#include <cstdio>#include <stdlib.h>using namespace std;struct Node {double coef;int expn;Node *next;};void CreatPolynomial(Node *&head, int n)        //生成带表头结点的单链表，除头结点外另生成n个结点  {head = (Node *)malloc(sizeof(Node));head->coef = 0;head->expn = 0;head->next = NULL;                           //初始化头结点  cout << "请输入各项系数及指数:"<< endl;Node *p = head;for(int i = 0; i < n; i++) {p->next = (Node *)malloc(sizeof(Node));  //生成新结点，尾插入生成链表  p = p->next;cin >> p->coef >> p->expn;p->next = NULL;}}void PrintPolynomial(Node *&head){if(head->next == NULL)                            //结果是0时直接输出0  putchar('0');    else {for(Node *p = head->next; p != NULL; p = p->next){  if(p != head->next && p->coef >0)        //当p非首项且指向的系数为正时才输出'+'  putchar('+');                        //之前只判定了p->coef >0                  if(p->coef == 1){                       //系数为1或-1时特殊处理  if(p->expn == 0)putchar('1');                   //判断条件不能写在一起：  }                                      //if(p->coef == 1 && p->expn == 0) putchar('1');  else if(p->coef == -1)putchar('-');elsecout << p->coef;              switch(p->expn){                        //指数为0或1时特殊处理              case 0:break;                case 1:putchar('x');break;                default:p->expn < 0 ? printf("x^(%d)", p->expn) : printf("x^%d", p->expn);  //  指数小于0时打括号  break;}}}cout << endl;}  void Free(Node *&head){Node *q = NULL;for(Node *p = head; p != NULL; p = q){q = p->next;free(p);}}char cmp(int a, int b){if(a > b)return '>';if(a < b)return '<';return '=';}void AddPolynomial(Node *&pA, Node *&pB)        //传进两个链表的头指针  {Node *ha = pA;Node *hb = pB;Node *qa = ha->next;                     //ha, hb分别跟在qa, qb的后一位置  Node *qb = hb->next;                     //qa, qb分别指向Pa, Pb中当前比较元素  while(qa && qb){double sum = 0;int a = qa->expn;int b = qb->expn;switch( cmp(a, b) ){              case '<':ha = qa;qa = qa->next;                       //非ha = ha->next;  break;              case '=':sum = qa->coef + qb->coef;if(sum != 0.0) {qa->coef = sum;ha = qa;       }else {if(ha->next != qa)cout << "Error: ha->next != qa" << endl;ha->next = ha->next->next;     //删除和为0的结点，ha不变，还在qa后一位置  free(qa);}if(hb->next != qb)cout << "Error: hb->next != qb" << endl;hb->next = hb->next->next;free(qb);qb = hb->next;qa = ha->next;break;              case '>':hb->next = hb->next->next;         //删除qb指向的结点  qb->next = ha->next;              //将qb插入ha后qa前  ha->next = qb;              qb = hb->next;                       //not qb = ha->next  ha = ha->next;break;              default:cout << "Error!" << endl;break;}}if(qb)ha->next = qb;free(hb);}  int main(){                                             //freopen("cin.txt", "r", stdin);  Node *A = NULL;Node *B = NULL;int lenA;int lenB;while(cout << "请输入A的项数：" << endl, cin >> lenA) {CreatPolynomial(A, lenA);                   //生成A链表         cout << "请输入B的项数：" << endl;         //生成B链表  cin >> lenB;CreatPolynomial(B, lenB);          cout << " A = ";                          //输出A链表  PrintPolynomial(A);cout << " B = ";                          //输出B链表  PrintPolynomial(B);          AddPolynomial(A, B);                        //A = A + B  cout << "A+B= ";PrintPolynomial(A);                         //输出和  cout << endl;          Free(A);                                    //务必释放结点  }return 0;}