CODEWITHSUNDEEP
c++liststack
Imaginary Boo
Imaginary Boo

Reputation: 33

String turned into a linked list then checking parentheses balance

So as an assignment I have to get a string from the user and turn it into a list and then check parentheses balance. However, I keep getting `warning: control reaches end of non-void function [-Wreturn-type] 

#include<iostream>
#include<string>
#include<stacks>
class Node{
public:
char data;
Node *head;
Node *tail;
Node *next;
Node *node;

void addToList(char);
bool CheckList();
void StringToList(string, Node*);
};
Node* addToList(char data)
    {
        Node* newNode = new Node;
        newNode->data = data;
        newNode->next = NULL;
        return newNode;
};

Node* StringToList(string text, Node* head)
{
    head = addToList(text[0]);
    Node *CurrentNode = head;
    for (int i = 1; i <text.size(); i++){
        CurrentNode->next = addToList(text[i]);
        CurrentNode = CurrentNode->next;
    }
    return head;
}
bool CheckList(Node* head)
{
    char c;

    stack <char> p;
    int i = 0;
    Node* CurrentNode = head;
    while(CurrentNode != NULL){

        if('(' || '{' || '['== CurrentNode->data){
            p.push(CurrentNode->data);

                 if(')' == CurrentNode->data){
                c= p.top();
                p.pop();
                if (c == '{' || c == '['){
                    return false;

            }
        }
            else if('}' == CurrentNode->data){
                c= p.top();
                p.pop();
                if (c == '(' || c == '['){
                    return false;

            }
        }
            else if('}' == CurrentNode->data){
                c= p.top();
                p.pop();
                if (c == '(' || c == '['){
                    return false;

                }
        }



            }
    }
    CurrentNode = CurrentNode->next;


}

int main()
{
    string text = "(check)[";
    Node *head = NULL;

    head = StringToList(text, head);
    if(CheckList(head)){
        cout<<"MAMA MIA IT WORKED-A!";
    }
    else
        cout<<"IT'S-A STILL WORKING!!!";

    return 0;

}

Any help would be appreciated. Thank you again for your time. Also, sorry if my code looks a bit messy but im kind of new to stacks and lists.

Upvotes: 3

Views: 211

Answers (2)

Paul Evans
Paul Evans

Reputation: 27567

Your function:

bool CheckList(Node* head)

doesn't have a return at the end:

    }
    CurrentNode = CurrentNode->next;


}

you must return something:

    }
    CurrentNode = CurrentNode->next;

    return /* an appropriate boolean value */;
}

Upvotes: 3

walnut
walnut

Reputation: 22152

CheckList claims to return a bool, but after the while loop and

CurrentNode = CurrentNode->next;

you don't have a return statement. The function just ends without returning a value. If a call to a function with non-void return type ends without a return statement (or prior exit via exception), the program has undefined behavior. The compiler is warning you about this possibility.

You need to add a return statement at the end of the function, with the value that you want to return. Given that the other return statements in the function all return false, I would assume that you intend to return true if the whole loop executed without returning false:

CurrentNode = CurrentNode->next;
return true;

Upvotes: 3

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