多项式导数计算器 c++ 中的问题

Question

I am doing a project for my school its a polynomial derivative calculator in c++ and I am having these problems:

( ^ is Exponentiation)

1. when user types -x^n it does not calculate the - in the outcome ex: -x^4 -> 4x^3

2. when user types x^n for a second time, or in a polynomial, it goes like this: 2x^5+x^4 -> 10x^4+0x^3

int main()
{
    char s[100];
    cout << " enter your Polynomial :  (use ^ for Exponentiation) ";
    cin.getline(s, 100, '\n');

    int i = 0;
    char za[20], t[20], z[20];
    
    while (true) {

        
        if (s[i] == '\0') {
            break;
        }

        if (s[i] == '-' && s[i + 1] == 'x') {
            i += 2;
            if (s[i] == '^') {
                i++;
                int j = 0;

                if (s[i] == '-') {                 

                    for (j, i; s[i] != '+' && s[i] != '\0'; i++, j++) {

                        if (j != 0) {

                            if (s[i] == '-')
                                break;
                        }

                        t[j] = s[i];

                    }

                    t[j] = '\0';


                }
                else {

                    for (j, i; s[i] != '+' && s[i] != '-' && s[i] != '\0'; i++, j++) {

                        t[j] = s[i];
                    }
                    t[j] = '\0';

                }
                float tavan = atof(t);



                if (s[(i - j) - 3] == '+') {

                    cout << '+' << tavan << "x^" << tavan - 1;
                }
                else {
                    cout << tavan << "x^" << tavan - 1;
                }
                continue;

            }
            else {

                cout << "-1";
                continue;
            }
        }
         if (s[i] == 'x') {
             i++;
            if (s[i] == '^') {
                i++;
                int j = 0;

                if (s[i] == '-') {                

                    for (j, i; s[i] != '+' && s[i] != '\0'; i++, j++) {

                        if (j != 0) {

                            if (s[i] == '-')
                                break;
                        }

                        t[j] = s[i];

                    }

                    t[j] = '\0';
                

                }
                else {
                    
                    for (j, i; s[i] != '+' && s[i] != '-' && s[i] != '\0'; i++, j++) {

                        t[j] = s[i];
                    }
                    t[j] = '\0';

                }
                float tavan = atof(t);

                

                if (s[(i-j)-2] == '+') {
                    
                    cout << '+' << tavan << "x^" << tavan - 1;
            }
                else {
                    cout << tavan << "x^" << tavan - 1;
                }
                continue;
            }

            else {
                if (s[i - 2] == '+') {
                    cout << '+' <<"1";
                }
                else {
                    cout << "1";
                }
                continue;
            }
        }
        else {
            int x = 0;
            
            for (x, i; s[i] != '^'; i++, x++) {

                z[x] = s[i];

            }
            z[x] = '\0';
            i++;

            int j = 0;


            if (s[i] == '-') {                

                for (j, i; s[i] != '+' && s[i] != '\0'; i++, j++) {

                    if (j != 0) {
                        if (s[i] == '-')
                            break;
                    }

                    t[j] = s[i];

                }

                t[j] = '\0';

            }
            else {

                for (j, i; s[i] != '+' && s[i] != '-' && s[i] != '\0'; i++, j++) {

                    t[j] = s[i];
                }
                t[j] = '\0';

            }


            int k = 0;
            for (k; z[k] != 'x'; k++) {

                za[k] = z[k];

            }
            za[k] = '\0';

        

        float zarib = atof(za);
        float tavan = atof(t);

        zarib = tavan * zarib;
        tavan = tavan - 1;

        if (z[0] == '+') {

            cout << '+' << zarib << "x^" << tavan;
        }
        else {
            cout << zarib << "x^" << tavan;

        }

    }

    }

    return 0;
}

Answer 1

I recommend that you use list to make it easier to insert data. Also, a better structured code will be helpful to find problems. You could refer to the following code;

typedef struct node
{
    float coef;
    int expn;
    struct node* next;
} PLOYList;

void insert(PLOYList *head, PLOYList *input)
{
    PLOYList *pre, *now;
    int signal = 0;
    pre = head;
    if (pre->next == NULL)
    {
        pre->next = input;
    }
    else
    {
        now = pre->next;
        while (signal == 0)
        {
            if (input->expn < now->expn)
            {
                if (now->next = NULL)
                {
                    now->next = input;
                    signal = 1;
                }
                else
                {
                    pre = now;
                    now = pre->next;
                }
            }
            else if (input->expn > now->expn)
            {
                input->next = now;
                pre->next = input;
                signal = 1;
            }
            else
            {
                now->coef = now->coef + input->coef;
                signal = 1;
                free(input);
                if (now->coef == 0)
                {
                    pre->next = now->next;
                    free(now);
                }
            }
        }
        
    }
}

PLOYList *create(char ch)
{
    PLOYList *head, *input;
    float x;
    int y;
    head = (PLOYList*)malloc(sizeof(PLOYList));
    head->next = NULL;
    scanf("%fx^ %d+", &x, &y);
    while (x != 0)
    {
        input = (PLOYList*)malloc(sizeof(PLOYList));
        input->coef = x;
        input->expn = y;
        input->next = NULL;
        insert(head, input);
        scanf("%fx^%d+", &x, &y);
    }
    return head;
}

PLOYList *def(PLOYList *head)
{
    PLOYList *p;
    p = head->next;
    while (p)
    {
        p->coef = p->expn;
        p->expn = p->expn--;
        p = p->next;
    }
    return head;
}

void print(PLOYList *fun)
{
    PLOYList *printing;
    int flag = 0;
    printing = fun->next;
    if (fun->next == NULL)
    {
        printf("0\n");
    }
    while (flag == 0)
    {
        if (printing->coef > 0 && fun->next != printing)
            printf("+");
        if (printing->coef == 1);
        else if (printing->coef == -1)
            printf("-");
        else
            printf("%f", printing->coef);
        if (printing->expn != 0)
            printf("x^%d", printing->expn);
        else if ((printing->coef == 1) || (printing->coef == -1))
            printf("1");
        if (printing->next == NULL)
            flag = 1;
        else
            printing = printing->next;
    }
    printf("\n");

}