Problem with reducing the amount of code on my if statement - c

Question

I'm writing my first C program and there's not a single way I can figure out how I can reduce the size of my if statements, for some reason I think that its a little too long. I have tried reducing the lines of code, playing with it but when I change something some messages when I test it don't appear such as Purchase was successful or it failed. I know that this is a little of a beginner question. Could you help me out and if possible give any tips on what to use and research to make it more concise?
if (input == 'A') {
calculation = budget - apple;
if (calculation >= 0) {
printf("Purchase was a success!\n");
printf("Purchase details\n");
printf("----------------------\n");
printf("Item: %c\n", input);
printf("Price: \x9C%.2f\n", apple);
printf("Remaining budget: \x9C%.2f\n\n", calculation);
printf("Thanks for shopping with us!");
}
else {
printf("Purchase FAILED!\n");
printf("Low budget or invalid item!\n\n");
printf("Thanks for shopping with us!");
}
} else if (input == 'O') {
calculation = budget - orange;
if (calculation >= 0) {
printf("Purchase was a success!\n");
printf("Purchase details\n");
printf("----------------------\n");
printf("Item: %c\n", input);
printf("Price: \x9C%.2f\n", orange);
printf("Remaining budget: \x9C%.2f\n\n", calculation);
printf("Thanks for shopping with us!");
}
else {
printf("Purchase FAILED!\n");
printf("Low budget or invalid item!\n\n");
printf("Thanks for shopping with us!");
}
} else if (input == 'P') {
calculation = budget - pear;
if (calculation >= 0) {
printf("Purchase was a success!\n");
printf("Purchase details\n");
printf("----------------------\n");
printf("Item: %c\n", input);
printf("Price: \x9C%.2f\n", pear);
printf("Remaining budget: \x9C%.2f\n\n", calculation);
printf("Thanks for shopping with us!");
}
else {
printf("Purchase FAILED!\n");
printf("Low budget or invalid item!\n\n");
printf("Thanks for shopping with us!");
}
} else {
printf("Purchase FAILED!\n");
printf("Low budget or invalid item!\n\n");
printf("Thanks for shopping with us!");
};

Answer 1

Create a temporary variable (e.g. fruits), and use input to determine what it should be set to, using an otherwise impossible value for "invalid item", like:
if (input == 'A') {
fruits = apple;
} else if (input == 'O')
fruits = orange;
} else if (input == 'P') {
fruits = pear;
} else {
fruits = -1; // Invalid item
}
Once that's done the rest can become:
if(fruits != -1) {
calculation = budget - fruit;
if (calculation >= 0) {
printf("Purchase was a success!\n");
printf("Purchase details\n");
printf("----------------------\n");
printf("Item: %c\n", input);
printf("Price: \x9C%.2f\n", fruits);
printf("Remaining budget: \x9C%.2f\n\n", calculation);
printf("Thanks for shopping with us!");
} else {
fruits = -1; // Low budget or invalid item!
}
}
if(fruits == -1) {
printf("Purchase FAILED!\n");
printf("Low budget or invalid item!\n\n");
printf("Thanks for shopping with us!");
}

Answer 2

Expanding upon the concepts of the posted solution, one might consider that "insufficient funds" and "item does not exist" to require different messages. It is also possible to determine based on the chosen fruit, if the user has the funds needed, or if the user indeed has insufficient funds to purchase ANY fruit at all.
To allow for additional fruit items, we can use arrays:
#include <stdio.h>
#define MAXLINE 80
#define WALLET 10.00
typedef struct {
int id;
double cost;
} Product;
int main() {
char buffer[MAXLINE];
double balance = WALLET;
Product pricelist[] = {
{0, 0.00}, {1, 1.45}, {2, 1.16}, {3, 1.23}
};
char* fruit[] = {"", "Apple", "Orange", "Pear"};
size_t itemcount = (sizeof(pricelist)/sizeof(Product));
double low_price = pricelist[1].cost;
while (1) {
int choice = 0;
printf("Price List:\n");
for (size_t i = 1; i < itemcount; ++i) {
double c = pricelist[i].cost;
printf("%d: %s\t\%.2f\n", i, fruit[i], c);
low_price = c < low_price ? c : low_price;
}
printf("Your balance is: %.2f. Enter Selction: ", balance);
if (fgets(buffer, MAXLINE, stdin) != NULL) {
sscanf(buffer, "%d", &choice);
}
if (choice > 0 && choice < itemcount) {
Product p = pricelist[choice];
if (balance - p.cost >= 0.00) {
balance -= p.cost;
printf("\nPurchase was a success!\n");
printf("Purchase details\n");
printf("----------------------\n");
printf("Item: %s\n", fruit[choice]);
printf("Price: \x9C%.2f\n", p.cost);
printf("Remaining budget: \x9C%.2f\n\n", balance);
}
else {
printf("\nPurchase FAILED!\n");
printf("Insufficient funds, sorry.\n\n");
}
}
else {
printf("Choice not recognized, please try again\n\n", choice);
}
if (balance <= low_price ) {
printf("You can make no further purchases\n");
break;
}
}
printf("Thanks for shopping with us!\n");
}