一元多项式（具有非负次幂）的数组实现

/* poly.h */

#ifndef _POLY_H
#define _POLY_H

#define MAXDEGREE    10

struct poly
{
    int coefarray[MAXDEGREE + 1];
    int highpower;
};

void zero_poly(struct poly *p);
void print_poly(const struct poly *p);
void add_poly(const struct poly *p1, const struct poly *p2, struct poly *psum);
void mult_poly(const struct poly *p1, const struct poly *p2, struct poly *pprod);

#endif

/* poly.c */

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

void zero_poly(struct poly *p)
{    
    int i;    
        
    for( i = 0; i <= MAXDEGREE; i++)
        p->coefarray[i] = 0;
    p->highpower = 0;
}

void print_poly(const struct poly *p)
{
/*    
    int i;

    for(i = p->highpower; i >= 0; i--)
        printf("%d ", p->coefarray[i]);

    printf("\n");
*/
    int i, hp;
    hp = p->highpower;
    if(p->coefarray[hp] != 1)    
        printf("%dx^%d", p->coefarray[hp], hp);
    else    
        printf("x^%d", hp);

    for(i = hp - 1; i >= 1; i--)
    {
        if(p->coefarray[i] != 0)
        {
            if(p->coefarray[i] != 1)
                printf(" + %dx^%d", p->coefarray[i], i);

         else
                printf(" + x^%d", i);
        }
    }
    if(p->coefarray[0] != 0)
        printf(" + %d", p->coefarray[0]);
    printf("\n");
}
void add_poly(const struct poly *p1, const struct poly *p2, struct poly *psum)
{
    int i;
    int ph1, ph2;

    ph1 = p1->highpower;
    ph2 = p2->highpower;

    psum->highpower = ph1 > ph2 ? ph1 : ph2;

    for(i = psum->highpower; i >= 0; i--)
    {
        psum->coefarray[i] = p1->coefarray[i] + p2->coefarray[i];
    }
}

void mult_poly(const struct poly *p1, const struct poly *p2, struct poly *pprod){
    int i, j;
    
    zero_poly(pprod);

    pprod->highpower = p1->highpower + p2->highpower;

    if(pprod->highpower > MAXDEGREE)
    {
        printf("exceeded array size\n");
        exit(1);
    }

    for(i = 0; i <= p1->highpower; i++)
        for(j = 0; j <= p2->highpower; j++)
            pprod->coefarray[i+j] += p1->coefarray[i] * p2->coefarray[j];
}

/* poly_test.c */

#include "poly.h"
#include <stdio.h>

int
main(void)
{
    struct poly p1, p2, psum, pmult;

    zero_poly(&p1);
    zero_poly(&p2);

    p1.highpower = 2;
    p1.coefarray[2] = 1;
    
    p2.highpower = 3;
    p2.coefarray[3] = 1;
    p2.coefarray[2] = 2;
    p2.coefarray[1] = 1;
    p2.coefarray[0] = 1;

    printf("p1      = ");
    print_poly(&p1);
    printf("p2      = ");
    print_poly(&p2);
    
    add_poly(&p1, &p2, &psum);
    printf("p1 + p2 = ");
    print_poly(&psum);
    
    mult_poly(&p1, &p2, &pmult);
    printf("p1 * p2 = ");
    print_poly(&pmult);
}

运行结果如下：