Can't decode a polynomial properly

#include<stdio.h>
#include<stdlib.h>
#define TRUE 1
#define FALSE 0

typedef struct polynomial{
    int coeff;
    char var;
    int exp;
    struct polynomial *link;
} poly;

poly* decode(char*);

main()
{
    char polynomial[100];
    poly *first, *second;

    printf("\n---Enter 1st polynomial---\n\n");
    scanf("%s",polynomial);
    first=decode(polynomial);

    printf("\n---Enter 2nd polynomial---\n\n");
    scanf("%s",polynomial);
    second=decode(polynomial);

    //More statements further

return 0;
}

/*--- Decoding Polynomial ---*/

poly* decode(char *polynomial)
{
    poly *p=NULL, *q=NULL, *temp=NULL;
    int i=0, sign;
    short coeff_entry=TRUE, exp_entry=FALSE, var_visited=FALSE, exp_visited=FALSE, coeff_visited=FALSE;

    while(polynomial[i]!='\0') 
    {

        temp=(poly*)malloc(sizeof(poly));
        if(!temp)
        {
            printf("Error! Memory not allocated\n");
            exit(1);
        }

        if(polynomial[i]==43) {i++; sign=1;}
        if(polynomial[i]==45) {i++; sign=-1;}
        while(1)
        {
            if((polynomial[i]>=48&&polynomial[i]<=57)&&coeff_entry==TRUE)
            {
                temp->coeff=10*(temp->coeff)+(polynomial[i]-48);
                coeff_visited=TRUE;
            }
            else if((polynomial[i]>=65&&polynomial[i]<=90)||(polynomial[i]>=97&&polynomial[i]<=122))
            {
                temp->var=polynomial[i];
                coeff_entry=FALSE;
                exp_entry=TRUE;
                var_visited=TRUE;
            }
            else if((polynomial[i]>=48&&polynomial[i]<=57)&&exp_entry==TRUE)
            {
                temp->exp=10*(temp->exp)+(polynomial[i]-48);
                exp_visited=TRUE;
            }
            else if(polynomial[i]==43||polynomial[i]==45||polynomial[i]=='\0')
            {
                exp_entry=FALSE;
                coeff_entry=TRUE;
                if(var_visited&&!exp_visited)
                {
                    temp->exp=1;
                    !var_visited;
                    !exp_visited;
                }
                if(!coeff_visited)
                {
                    !coeff_visited;
                    temp->coeff=1;
                }
                temp->coeff*=sign;              
                break;
            }
            i++;
        }

        //These lines are for debugging purpose only
        printf("\nCoefficient of the term is: %d\n",temp->coeff);
        printf("Variable of the term is: %c\n",temp->var);
        printf("Exponent of the term is: %d\n",temp->exp);

        temp->link=NULL;
        if(p==NULL)     p=q=temp;
        else
        {
            q->link=temp;
            q=q->link;
        }
    }

return p;
}

In my code I am asking user to input a polynomial in the form like: -5x^2+7y^3-19z+5



Everything seems fine but two problems in decoding this polynomial and storing in the linked list form:



First bug comes when the first-most coefficient is positive in polynomial like 17x^3-13z+5

In this case a very long integer value (most probably garbage value) gets store in the respected node of linked list.



Second bug is when there is no first coefficient like x^7-18y^3+z-13

In this case 0 gets stored in the respected node of linked list. In other terms of polynomial, like z in example above, where there is no coefficient 1 gets stored in the coeffient part of the node.



So problem arises with the first coefficient only that too a 'positive coeff' or 'no coefficient' at all.