linked list help

This is a discussion on linked list help within the C++ Programming forums, part of the General Programming Boards category; Code: struct BLOCK { vector <string> say; vector <string> resp; int index; BLOCK *next; }; BLOCK *first; BLOCK *curr; int ...

  1. #1
    i want wookie cookies the Wookie's Avatar
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    Oct 2002
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    linked list help

    Code:
    struct BLOCK {
    	vector <string> say;
    	vector <string> resp;
    	int index;
    	BLOCK *next;
    };
    
    BLOCK *first;
    	BLOCK *curr;
    
    int cAIBrain::GetWords(char *strWork, char type){
    	
    	string temp;
    	int numwords=0;
    	BLOCK *insert = new BLOCK;
    
    	//clear the >, so then the words are left
    	for(int i=0;i<=strlen(strWork);i++){
    		if(*strWork=='>')
    			break;
    		
    		*strWork++;
    	}
    
    	*strWork++;	//clear the >
    	while(*strWork!='/'){
    		//next time change this with the delimiter chosen
    		//by the user, for now it is a |
    		if(*strWork=='|' || *strWork=='<'){
    			*strWork++;
    
    			if(type=='s')	 {	//if its a say block, add it to the say
    				insert->say.push_back(temp);
    			} else if(type=='r'){	//if its a resp block, add it to resp
    				insert->resp.push_back(temp);
    			}
    
    			numwords+=1;
    			temp="";
    		} else {
    			temp += *strWork;
    		}
    
    		*strWork++; //move to next character
    	}
    
    	AddNode(insert);
        
    	return numwords;
    }
    
    
    void cAIBrain::AddNode(BLOCK *node) {
    	if(first==NULL){
    		first=node;
    	} else {
    		curr=first;
    
    		while(curr!=NULL){ 
    			curr=curr->next; //ERROR HERE!
    		}
    		curr=node;
    		curr->next = NULL;
    	}
    }
    I get an error in the "AddNode" function, that's the entire code. I think maybe my linked list implementation is off. I know its not optimized etc, I'm just trying to get it to work

    i set first to NULL in the class initialization, but ahh i cant figure it out


    thanks

  2. #2
    Code Goddess Prelude's Avatar
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    9,796
    It sounds as if you forgot to set node's next pointer to NULL, the memory location is indeterminate, so you get a segmentatin violation when you dereference the memory that your program doesn't own.

    -Prelude
    My best code is written with the delete key.

  3. #3
    i want wookie cookies the Wookie's Avatar
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    so before i add it, set the next to null?

    edit: did that, and did this:

    if(curr->next=NULL){
    curr->next=node;
    } else {

    while(curr->next!=NULL){
    curr=curr->next;
    }
    curr=node;
    curr->next = NULL;
    }

    i dont know what effect that will have yet on multiple blocks, but i'll see
    Last edited by the Wookie; 10-11-2002 at 04:08 PM.

  4. #4
    End Of Line Hammer's Avatar
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    >>if(curr->next=NULL){
    Only one equals sign...? I think you're meant to have 2
    When all else fails, read the instructions.
    If you're posting code, use code tags: [code] /* insert code here */ [/code]

  5. #5
    i want wookie cookies the Wookie's Avatar
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    ah, i am a fool.

    now i get the same error on the while loop

    "Unhandled exception at 0x0041cd33 in aimoduletest.exe: 0xC0000005: Access violation reading location 0xcdcdcdf1."

    i dohave next set as null, i dont see what the problem could be..


    another edit:

    i fixed that, now when i try to get <vector>.size(), i get a memory violation. is it because my list node isnt initialized properly?

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