Beginner in C: Can't properly printf first and last element in double array? - arrays

Question

I'm trying to display a Wish List on the command line. The user enters the cost of the item, the level of priority (1-3), and whether or not it has financing options (y/n). The inputted values are put in multiple arrays. After the user enters all their values, they're displayed in a table at the end.
Everything in my code works fine except when I try to printf the user inputed cost values (double itemCosts[numOfItems];) in the table. The first and last element don't print properly, even when I input the same price (6225.88) for all of them. The last element is just 0.000000. See included pic of table output.
I tried debugging the issue by separating the cost-related loops and compiling/running them as another file and the costs display correctly...so I'm thinking the bug is somewhere else, but I can't find it.
#define MAX_ITEMS 10
#include <stdio.h>
int main()
{
const double MIN_INCOME = 500, MAX_INCOME = 400000;
int numOfItems;
double netIncome, itemTotal;
double itemCosts[numOfItems];
int itemPriors[numOfItems];
char itemFinOps[numOfItems];
printf("+--------------------------+\n");
printf("+ Wish List Forecaster |\n");
printf("+--------------------------+\n\n");
// Prompt for net monthly income
do
{
printf("Enter your monthly NET income: $");
scanf("%lf", &netIncome);
if (netIncome < MIN_INCOME)
{
printf("ERROR: You must have a consistent monthly income of at least $500.00\n\n");
}
else if (netIncome > MAX_INCOME)
{
printf("ERROR: Liar! I'll believe you if you enter a value no more than $400000.00\n\n");
}
} while (!(netIncome >= MIN_INCOME && netIncome <= MAX_INCOME));
printf("\n");
// Prompt for # of wish list items
do
{
printf("How many wish list items do you want to forecast?: ");
scanf("%d", &numOfItems);
if (!(numOfItems > 0 && numOfItems <= MAX_ITEMS))
{
printf("ERROR: List is restricted to between 1 and 10 items.\n\n");
}
printf("\n");
} while (!(numOfItems > 0 && numOfItems <= MAX_ITEMS));
// Store wish list item details
for (int i = 0; i < numOfItems; i++)
{
printf("Item-%d Details:\n", i + 1);
do //////////////// ******** PROMPT COST ********** //////////
{
printf("Item cost: $");
scanf("%lf", &itemCosts[i]);
if (!(itemCosts[i] >= (double)100))
{
printf(" ERROR: Cost must be at least $100.00\n");
}
} while (!(itemCosts[i] >= (double)100));
do // prompt priority
{
printf("How important is it to you? [1=must have, 2=important, 3=want]: ");
scanf("%d", &itemPriors[i]);
if (!(itemPriors[i] >= 1 && itemPriors[i] <= 3))
{
printf(" ERROR: Value must be between 1 and 3\n");
}
} while (!(itemPriors[i] >= 1 && itemPriors[i] <= 3));
do // prompt finance options
{
printf("Does this item have financing options? [y/n]: ");
scanf(" %c", &itemFinOps[i]);
if (!(itemFinOps[i] == 'y' || itemFinOps[i] == 'n'))
{
printf(" ERROR: Must be a lowercase 'y' or 'n'\n");
}
} while (!(itemFinOps[i] == 'y' || itemFinOps[i] == 'n'));
printf("\n");
}
///////// display summary of item details in TABLE //////////
printf("Item Priority Financed Cost\n");
printf("---- -------- -------- -----------\n");
for (int j = 0; j < numOfItems; j++)
{
printf(" %d %d %c %lf\n", j + 1, itemPriors[j], itemFinOps[j], itemCosts[j]);
itemTotal += itemCosts[j];
}
return 0;
}

Answer 1

int numOfItems;
double netIncome, itemTotal;
double itemCosts[numOfItems];
int itemPriors[numOfItems];
char itemFinOps[numOfItems];
It is undefined behaviour as your numOfItems is not inilized. In C table will not grow or shrink to the size when you change this variable
Change to:
double itemCosts[MAX_ITEMS];
int itemPriors[MAX_ITEM];
char itemFinOps[MAX_ITEM];
Always check the result of scanf. Exmaple:
if(scanf("%lf", &netIncome) != 1){ /* handle error*/}

Answer 2

As Vlad from Moscow and 0___________ said, you cannot define an array using a not initialised variable for the number of its elements. You can define the variables as
double *itemCosts;
int *itemPriors;
char *itemFinOps;
and after the variable numOfItems is given a value, you dynamically allocate memory as follows:
itemCosts = (double*) malloc(numOfItems * sizeof(double));
itemPriors = (int*) malloc(numOfItems * sizeof(int));
itemFinOps = (char*) malloc(numOfItems * sizeof(char));
or
itemCosts = (double*) calloc(numOfItems, sizeof(double));
itemPriors = (int*) calloc(numOfItems, sizeof(int));
itemFinOps = (char*) calloc(numOfItems, sizeof(char));
calloc initialises all elements of array to 0
At the end you must free the allocated memory:
free(itemCosts);
free(itemPriors);
free(itemFinOps);