c 中的多项式乘法

Question

我正在尝试用 C 创建一个多项式乘法程序，其中我实现了一个名为

pmult

的函数，用于两个多项式的乘法。该程序运行良好，直到需要为相同的指数值添加多项式。在这个阶段，我遇到了分段错误，并显示错误消息：

malloc(): corrupted top size

我该怎么办？

Example i used:
p1:
No. of elements=5
coeff expo
2     6  
5     3
3     2
2     1
3     0
Example i used:
p2:
No. of elements=5
coeff expo
3     7  
2     6
5     4
3     2
7     0

这是源代码：

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

typedef struct poly{
    int coeff;
    int expo;
} poly;

poly *pmult(poly *p1, poly *p2, int term1, int term2, int term, int *ptr);
poly *create(int term);
void display(poly *p, int term);

poly *create(int term)
{
    poly *p = malloc(term * sizeof(poly));
    for (int i = 0; i < term; i++)
    {
        printf("Enter the coefficient and the exponent of the polynomial:");
        scanf("%d%d", &p[i].coeff, &p[i].expo);
    }
    return p;
}

poly *pmult(poly *p1, poly *p2, int term1, int term2, int term, int *ptr)
{
    poly *p3 = malloc(term * sizeof(poly));
    int k = 0;
    
    for (int i = 0; i < term1; i++)  //Multiplies every poly1's term with every poly2's term and stores them in poly3
    {
        for (int j = 0; j < term2; j++)
        {
            p3[k].coeff = p1[i].coeff * p2[j].coeff;
            p3[k++].expo = p1[i].expo + p2[j].expo;
        }
    }
    
    printf("Displaying poly3:\n");
    display(p3, k);
    int max = p3[0].expo;
    
    for (int i = 1; i < k; i++)
    {
        if (p3[i].expo > max)
        {
            max = p3[i].expo;
        }
    }
    
    printf("\nMAXXXXX..........:%d\n", max);
    int h = 0;
    poly *p4 = malloc(k * sizeof(poly));
    
    for (int i = max; i >= 0; i--)  //if we have a polynomial result as 3X5+4X3+6X3+7X3+3X3+0X2 so we need to format it as 3X5+20X3+0X2
    {
        int sum = 0;
        for (int j = 0; j < k; j++)
        {
            if (i == p3[j].expo)
            {
                sum += p3[j].coeff;
            }
        }
        if (sum > 0)
        {
            p4[h].expo = i;
            p4[h++].coeff = sum;
        }
    }
    
    free(p3);
    *ptr = h;
    return p4;
}

void display(poly *p, int term)
{
    printf("Printing a polynomial......\n");
    for (int i = 0; i < term; i++)
    {
        printf("%dX%d + ", p[i].coeff, p[i].expo);
    }
    printf("\n");
}

int main()
{
    int termp1, termp2;
    
    printf("Enter the no of terms in polynomial one:");
    scanf("%d", &termp1);
    
    poly *poly1 = create(termp1);
    display(poly1, termp1);
    
    printf("Enter the no of terms in polynomial one:");
    scanf("%d", &termp2);
    poly *poly2 = create(termp2);
    
    display(poly2, termp2);
    
    int term = termp1 + termp2;
    int ptr = 0;
    
    poly *poly3 = pmult(poly1, poly2, termp1, termp2, term, &ptr);
    
    display(poly3, ptr);
    
    return 0;
}

Answer 1

计算多项式乘积的方法需要临时存储

termp1 * termp2

项，而不是预期的

termp1 + termp2

最大值。根据 C 库的报告，存储某些计算项时会出现缓冲区溢出、调用未定义的行为、破坏内存分配数据。