insert function is doesn't add a new elements [closed] - c++

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I wrote a program which should to insert elements in the list compare with their costs, but it doesn't work. I enter one element and then program doesn't work. And I can't understand what's wrong.
here is an exactly the exercise:
Modify the list, so elements on the list are ordered by price. New items added to the list should be inserted into the right place
#include <iostream>
#include <string>
using namespace std;
typedef struct listt
{
string name;
float price;
struct listt *next;
}listt;
typedef listt* listPtr;
void insertt(listPtr *, string, float);
void printList(listPtr);
void instruct();
int main()
{
unsigned int choice;
float costs;
string itemName;
listPtr head = NULL;
instruct();
cin >> choice;
while(choice != 3)
{
switch(choice)
{
case 1:
cout << "Please enter the name of the item:" << endl;
cin >> itemName;
cout << "Please enter the cost of item: " <<endl;
cin >> costs;
insertt(&head, itemName, costs);
break;
case 2:
printList(head);
break;
}
cout<<"Choose the operation\n";
cin >> choice;
}
cout<<"end of operation";
return 0;
}
void instruct(void)
{
cout<<"Choose the operation\n" << "1.Fill the list\n" << "2.Print the list\n" << "3.End operation\n";
}
void insertt(listPtr *itemList, string nm, float cst)
{
listPtr previousPt;
listPtr currentPt;
listPtr newPtr;
if(newPtr != NULL){
newPtr->name = nm;
newPtr->price = cst;
newPtr->next = *itemList;
}
previousPt = NULL;
currentPt = *itemList;
while(currentPt != NULL && cst > currentPt->price )
{
previousPt = currentPt;
currentPt = currentPt->next;
}
if(currentPt == NULL)
{
newPtr->next = *itemList;
*itemList = newPtr;
} else{
previousPt->next = newPtr;
newPtr->next = currentPt;
}
}
void printList(listPtr hh)
{
while(hh->next != NULL)
{
cout << hh->name <<" " << hh->price<< endl;
hh = hh->next;
}
}

Answer 1

in insertt :
void insertt(listPtr *itemList, string nm, float cst)
{
listPtr previousPt;
listPtr currentPt;
listPtr newPtr;
if(newPtr != NULL){
newPtr->name = nm;
newPtr->price = cst;
newPtr->next = *itemList;
}
newPtr is not initialized but you compare its value to NULL then may be modify an unknown block of memory, this is an undefined behavior
replace listPtr newPtr; by listPtr newPtr = new listt;
That comes because of typedef listt* listPtr; hidding the pointer, do not define typedef hiding pointer, this is always a source of problem
Your way to insert the new cell is wrong, for instance if the second insert cell as a lower price than the first you have an illegal memory access. A working solution is :
void insertt(listt ** itemList, string nm, float cst)
{
listt * newCell = new listt;
newCell->name = nm;
newCell->price = cst;
newCell->next = nullptr;
if (*itemList == nullptr)
*itemList = newCell;
else {
for (;;) {
if (cst < (*itemList)->price) {
newCell->next = *itemList;
*itemList = newCell;
return;
}
if ((*itemList)->next == nullptr) {
(*itemList)->next = newCell;
return;
}
itemList = &(*itemList)->next;
}
}
}
Note printList is erroned because the last element is never print, replace
while(hh->next != NULL)
by
while(hh != NULL)
or better
while(hh != nullptr)
Your struct listt is defined like in C
You need also to check your input are valid, your cin >> x; must be if (! (cin >> x)) { ..error management .. }