c语言构造两个按指数递增的有序链表，实现两个一元多项式相加

以下是C语言实现两个按指数递增的有序链表，实现两个一元多项式相加的代码：

#include <stdio.h>
#include <stdlib.h>

typedef struct node {
    int coef; // 系数
    int expn; // 指数
    struct node *next;
} Node, *Polynomial;

void CreatePolyn(Polynomial *P, int m) {
    *P = (Polynomial) malloc(sizeof(Node));
    (*P)->next = NULL;
    Node *r = *P;
    for (int i = 0; i < m; i++) {
        Node *p = (Node *) malloc(sizeof(Node));
        scanf("%d %d", &p->coef, &p->expn);
        p->next = NULL;
        r->next = p;
        r = p;
    }
}

void AddPolyn(Polynomial *Pa, Polynomial *Pb) {
    Node *p = (*Pa)->next, *q = (*Pb)->next, *r = *Pa;
    while (p && q) {
        if (p->expn < q->expn) {
            r->next = p;
            r = p;
            p = p->next;
        } else if (p->expn > q->expn) {
            r->next = q;
            r = q;
            q = q->next;
        } else {
            p->coef += q->coef;
            if (p->coef != 0) {
                r->next = p;
                r = p;
            } else {
                Node *temp = p;
                p = p->next;
                free(temp);
            }
            Node *temp = q;
            q = q->next;
            free(temp);
        }
    }
    r->next = p ? p : q;
    free(*Pb);
}

void PrintPolyn(Polynomial P) {
    Node *p = P->next;
    int flag = 0;
    while (p) {
        if (flag == 0) {
            printf("%d %d", p->coef, p->expn);
            flag = 1;
        } else {
            if (p->coef > 0) {
                printf(" + %d %d", p->coef, p->expn);
            } else {
                printf(" - %d %d", -p->coef, p->expn);
            }
        }
        p = p->next;
    }
    printf("\n");
}

int main() {
    Polynomial Pa, Pb;
    int m, n;
    scanf("%d", &m);
    CreatePolyn(&Pa, m);
    scanf("%d", &n);
    CreatePolyn(&Pb, n);
    AddPolyn(&Pa, &Pb);
    PrintPolyn(Pa);
    return 0;
}