用两个线性链表分别存储两个一元多项式，试实现两个多项式的加法/减法运算。 [基本要求] 一元多项式用链式存储结构实现存储； 注意： 1、多项式表的链表定义方法 2、注意临界状态的处理。的源代码

以下C++实现：

#include <iostream>
using namespace std;

// 定义多项式的项
typedef struct PolyNode {
    float coef; // 系数
    int expn; // 指数
    struct PolyNode *next; // 指向下一项的指针
} PolyNode, *Polynomial;

// 创建多项式
void createPoly(Polynomial &p) {
    p = (PolyNode *) malloc(sizeof(PolyNode)); // 创建头结点
    p->next = NULL;
    PolyNode *r = p; // r指向尾结点
    int n, e;
    float c;
    cout << "请输入多项式项数：";
    cin >> n;
    for (int i = 0; i < n; i++) {
        cout << "请输入第" << i + 1 << "项的系数和指数：";
        cin >> c >> e;
        if (c == 0) continue; // 忽略系数为0的项
        PolyNode *s = (PolyNode *) malloc(sizeof(PolyNode)); // 创建新结点
        s->coef = c;
        s->expn = e;
        r->next = s;
        r = s;
    }
    r->next = NULL;
}

// 多项式加法
void polyAdd(Polynomial pa, Polynomial pb, Polynomial &pc) {
    PolyNode *p1 = pa->next, *p2 = pb->next;
    PolyNode *pre = pc = pa; // pa作为结果多项式的头结点
    while (p1 && p2) {
        if (p1->expn == p2->expn) {
            float sum = p1->coef + p2->coef;
            if (sum != 0) {
                p1->coef = sum;
                pre->next = p1;
                pre = p1;
            } else {
                free(p1);
            }
            p1 = p1->next;
            PolyNode *tmp = p2;
            p2 = p2->next;
            free(tmp);
        } else if (p1->expn < p2->expn) {
            pre->next = p1;
            pre = p1;
            p1 = p1->next;
        } else {
            pre->next = p2;
            pre = p2;
            p2 = p2->next;
        }
    }
    pre->next = p1 ? p1 : p2;
    free(pb); // 释放pb的头结点
}

// 多项式减法
void polySub(Polynomial pa, Polynomial pb, Polynomial &pc) {
    PolyNode *p1 = pa->next, *p2 = pb->next;
    PolyNode *pre = pc = pa; // pa作为结果多项式的头结点
    while (p1 && p2) {
        if (p1->expn == p2->expn) {
            float diff = p1->coef - p2->coef;
            if (diff != 0) {
                p1->coef = diff;
                pre->next = p1;
                pre = p1;
            } else {
                free(p1);
            }
            p1 = p1->next;
            PolyNode *tmp = p2;
            p2 = p2->next;
            free(tmp);
        } else if (p1->expn < p2->expn) {
            pre->next = p1;
            pre = p1;
            p1 = p1->next;
        } else {
            PolyNode *s = (PolyNode *) malloc(sizeof(PolyNode)); // 创建新结点
            s->coef = -p2->coef;
            s->expn = p2->expn;
            pre->next = s;
            pre = s;
            p2 = p2->next;
        }
    }
    while (p2) { // 如果p2还有剩余项，全部加入结果多项式
        PolyNode *s = (PolyNode *) malloc(sizeof(PolyNode)); // 创建新结点
        s->coef = -p2->coef;
        s->expn = p2->expn;
        pre->next = s;
        pre = s;
        p2 = p2->next;
    }
    pre->next = p1; // 如果p1还有剩余项，全部加入结果多项式
    free(pb); // 释放pb的头结点
}

// 输出多项式
void printPoly(Polynomial p) {
    PolyNode *s = p->next;
    if (s == NULL) {
        cout << "0" << endl;
        return;
    }
    while (s) {
        if (s->coef > 0 && s != p->next) cout << "+";
        if (s->coef != 1 || s->expn == 0) cout << s->coef;
        if (s->expn > 0) cout << "x";
        if (s->expn > 1) cout << "^" << s->expn;
        s = s->next;
    }
    cout << endl;
}

int main() {
    Polynomial pa, pb, pc;
    createPoly(pa);
    createPoly(pb);
    cout << "多项式pa：";
    printPoly(pa);
    cout << "多项式pb：";
    printPoly(pb);
    polyAdd(pa, pb, pc);
    cout << "多项式pa + pb：";
    printPoly(pc);
    polySub(pa, pb, pc);
    cout << "多项式pa - pb：";
    printPoly(pc);
    return 0;
}

注：以上代码中的多项式加法和减法都是将结果存储在第一个多项式中，因此第二个多项式会被释放掉。如果需要保留第二个多项式，可以在函数内部创建一个新的多项式并将结果存储在其中。