C++ Notes: Struct Example 2

Problem - Product info

Let's use the Product struct, read into an array of Products, and sort by increasing price.

Global Declaration

Typically types are used in more than one function, and are therefore global or defined in an include file.

struct Product {
    char mfg_id[4];    // 4 char code for the manufacturer.
    char prod_id[8];   // 8-char code for the product
    int  price;        // price of the product in dollars.
    int  qty_on_hand;  // quantity on hand in inventory
};

Local Declarations

Product prods[1000]; // array to hold up to 1000 products
int n = 0;           // number of products in the array.

Reading the input

while (cin >> prods[n].mfg_id >> prods[n].prod_id
           >> prods[n].price  >> prods[n].qty_on_hand) {
    n++;
}

Sorting the array of products

Here's a simple bubble sort function that stops when there are no more exchanges. This is a fairly inefficient sort, and it's used here just as an example. Notice we can't compare the entire struct, only individual fields.

void bubbleSort2(Product pd[], int size) {
    bool doMore;
    do {
        doMore = false;  // assume this is last pass over array
        for (int i=0; i<size-1; i++) {
            if (pd[i].price > pd[i+1].price) {
                // exchange elements
                Product temp = pd[i]; pd[i] = pd[i+1]; pd[i+1] = temp;
                doMore = true;  // after exchange, must look again
            }
        }
    } while (doMore);
}