c++ - 循环链表计算多项式加法的问题

问题描述

用带头结点的循环链表求多项式加法，release版本下结果正确，debug版本下发生内存访问错误。个人觉得是代码有问题，调试运行后，问题出在delete(pb)，暂时注释delete后，又在Output函数内终止。看了好几遍感觉也没有逻辑问题，代码有点长，希望各位有时间能帮小弟解决一下，感激不尽！

#include<iostream>#include<stdlib.h>using namespace std;typedef int ElemType;typedef struct Lnode{ int quo; int deg; struct Lnode *next;}Lnode, *Linklist;//逆序创建循环链表，该循环链表的头指针指向最后一个节点void CreateList_L(Linklist &L, ElemType Q[], ElemType D[], int n){ L = NULL; Linklist s; for (int j = n - 1; j >= 0; --j) {s = new Lnode;s->deg = D[j];s->quo = Q[j];s->next = L;L = s; } s = new Lnode;//补充头结点 s->deg = 111111111; s->quo = 11111111; s->next = L; L = s; while (s->next != NULL) {s = s->next; } s->next = L; L = s;}//销毁链表void destory(Linklist &L){ Linklist p; p = L->next; while (p != L->next) {p = L; L = L->next; free(p); }}//输出线性表void Output(Linklist &L){ Linklist plist = L->next->next; while (plist != L->next) {cout << plist->quo << ' ';cout << plist->deg << ’n’;plist = plist->next; } cout << endl;}//两个多项式相加void Polyadd(Linklist &L, Linklist &P){ Linklist pa, pb, rc, qa, qb; pa = L->next->next; pb = P->next->next; rc = L->next; while (pa != L->next&&pb != P->next) {if (pa->deg<pb->deg)//pb指数大时，pb链接到rc中{ rc->next = pb; rc = pb; pb = pb->next;}else{ if (pa->deg>pb->deg)//pa指数大时，pa链接到rc中 {rc->next = pa; rc = pa; pa = pa->next; } else {if ((pa->quo + pb->quo) != 0)//如果系数相加不为零{ pa->quo = pa->quo + pb->quo; rc->next = pa; rc = pa; pa = pa->next; qb = pb; pb = pb->next; delete qb; qb = NULL;}//将pa中的系数值改为pa系数+pb系数，把pa链接到rc中，rc向后移动，用qb分别把pb结点记录下来，pa，pb向后移动，再将qb删除else//如果系数相加为零{ qa = pa; pa = pa->next; qb = pb; pb = pb->next; delete qa; qa = NULL; delete qb; qb = NULL;}//用qa，qb分别把pa，pb结点记录下来，pa，pb向后移动，再将qa，qb删除 }} } if (pb == P->next) {rc->next = pa; } else {rc->next = pb; pb = P->next; P->next = L->next; L = P; } delete(pb);//!!!!!!!!!!!!!删去此处也不可}int main(){ Linklist L, P; int n = 4; //ElemType Q1[]={5,9},D1[]={11,8}; ElemType Q1[] = { 5, 9, 3, 7 }, D1[] = { 11, 8, 1, 0 }; CreateList_L(L, Q1, D1, n); cout << '多项式L的系数和相应的次数分别为：' << endl; Output(L); int m = 2; ElemType Q2[] = { 9,5}, D2[] = { 8,1}; CreateList_L(P, Q2, D2, m); cout << '多项式P的系数和相应的次数分别为：' << endl; Output(P); Polyadd(L, P); cout << '多项式P+L的系数和相应的次数分别为：' << endl; Output(L); //destory(L); //destory(P);}

release下截图：

debug下截图：

问题解答

p = L; L = L->next; free(p);

你没有调用malloc, 不应该free的