C :: Linked List - Change Struct Pointers
Dec 17, 2013
I have a linked list where each node contains a pointer to a string, I'm treating the linked list as a text file and each node/string contains each line in the text file.
I have all of that working, but now I need to create a switchLine function that takes in the two line numbers and I need to switch those lines in the text file. I initially thought of switching the pointers to each the next node in the linked list such that the node order changes, but I then realized how much work that would actually take when you need to consider so many cases. So I instead thought of changing the pointers to strings. If I want to switch the 2nd and 3rd line, then I'd want to have the 2nd node in the list have its char * pointer point to the memory position that the 3rd node's char pointer points to, and vice versa.
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Feb 8, 2015
I'm having a little problem where after reading a file I'm unable to update my struct with some particular info. It is actually a linkedlist. This is my struct:
Code:
struct node{
int id;
char name[50];
struct node *next;
}*head;
And in my Main function:
Code:
int main(){
int i, t_id, num;
struct node *temp;
char name[50], t_name[50], input_name[50], line[LINESIZE], *value;
struct node *head = NULL;
FILE * ifp = fopen("AssignmentOneInput.txt", "r");
[Code] .....
Basically in the while loop when I input something like this for updating numbers:
Code: temp->id = num; //These are numbers separated by a comma. or this:
Code: strcpy(temp->name,value); //These are names The program crashes
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May 13, 2015
I've got an interface that provides the methods that are to be implemented
Code:
class A {
virtual void A() = 0;
}
class B : public A {
std::string operator<<(const std::string& lhs);
[Code] ....
I don't know why the << operator in B is never called..
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Mar 14, 2013
I need writing the function that makes change for an input number. Input a bunch of quarters, dimes, nickels, pennies, then in MAKE_CHANGE the amount per say (184) is input. So for 184cents, runs through quarters first using the quarters we have in the coinbox, and then goes to the next currency for the remaining 9cents
(184/25=7 184%25=9).
#include <cstdlib>
#include <iostream>
using namespace std;
struct coinbox {
int quarters;
int dimes;
[Code] .....
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Jan 17, 2014
the book I learn from gave a task to write a program which gets a matrix , and we have to write a function that switches 2 columns or rows the user inputs .as far as I know a function can not change variables in the main function without using pointers .so , theoretically, can a function described here can be written without using pointers ? as far as I tried - it can not.
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Mar 12, 2014
Im trying to take a previous project that was made with arrays and change it to a struct for storage.
Error2error LNK1120: 1 unresolved externalse:my documentsvisual studio 2013ProjectsConsoleApplication15DebugConsoleApplication15.exe11ConsoleApplication15
Error1error LNK2019: unresolved external symbol "void __cdecl getStudentInfo(class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > * const,int (* const)[5],float * const,char * const)" (?getStudentInfo@@YAXQAV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@QAY04HQAMQAD@Z) referenced in function _maine:my documentsvisual studio 2013ProjectsConsoleApplication15ConsoleApplication15Source.objConsoleApplication15
I've been trying to research this error message but I haven't been able to find much that pertains to the simple code I have.
Below it the first part of my c++ program that includes everything that I have changed before the error appeared. It seems to be centered around changing the void function at the end
#include <iostream>
#include <fstream>
#include <string>
#include <iomanip>
#include <climits>
using namespace std;
const int NUM_STUDENTS = 10;
const int NUM_SCORES = 5;
void getStudentInfo(string[], int[][NUM_SCORES], float[], char[]);
[code].....
The final line was originally
void getStudentInfo(string sn[], int ss[][NUM_SCORES], float sa[], char sg[]) {
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May 10, 2013
I am working on an assignment identical to another post from a couple years ago, for reference here is the thread:
array of pointers to structures sorting addresses by zip code
They way it is written on that thread is almost identical to the way the teacher implied to have it done (only wrote part of the input block). But I am having an error:
When it gets to the output section it outputs then next name along with the zip code... I tried strncpy and strxfrm but both cause more problems than they did work.
The last part of the project is to have the output put out in order of least zip code to most zip code (00000<99999), so this is causing me a real problem and I do not see what exactly is making this happen.
Here is my code (we dont HAVE to use gets but professor suggested using it for this assignment, next lab is to rewrite this using files and fgets rather than I/O redirection):
header.h Code: #ifndef lab_6b_7b_Header_h
#define lab_6b_7b_Header_h
//header file intiating other headers
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct{
[code]....
I have not started the sorting code because I cannot get past this, but once I have proper zip codes I am sure I can make a sort function no problem.
I am using xcode with some breaks to read variables as various points and do not notice anything wrong until it makes it to the output functions, although this page briefly pops up between input and output functions when the breaks are up:
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Mar 6, 2015
What I'm trying to do with this code is an address book and I have an array of pointers which are returned by malloc whenever I need to add an extra entry in the address book. What I need to do is search for a specific entry using bsearch. I've got an inqSort() function that sorts the table and runs normally, but my program crashes when I try to use bsearch.
Code:
typedef struct {
char name[20];
char phone[14];
} abEntry;
[Code] ....
Every time an entry is inserted, I inqsort() the array so it's always sorted, and it works as expected. But when I try to call findEntryUI(); from the main() function, the program crashes after entering the name I want to search.
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Mar 3, 2013
I am having problems with passing my values through functions.
Here is my code:
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
void test(int**);
void test2(int**);
[Code]....
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Jul 20, 2014
I'm quite new to C and these days I have been playing around with a linked list. I managed to make a working version using pointers, ad only for the sake of learning I was trying to do the same thing just passing the "Object reference" Here is the method that apparently doesn't work..
Code:
struct Node addNode(struct Node head){
int value;
struct Node *n;
printf("Please enter the value
");
scanf("%d", &value);
[Code]...
when I return the function i have something like: head=addNode(head)
Unfortunately it does not work the way I aspect. I suppose that there is something I have left out..
Code:
like n->next=&head
// passing the address of the head at the next pointer of the struct
head =*n
//copy the values of the new node to the old head..
There must be something wrong with this line.. return head; What have I done wrong?
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Apr 30, 2013
I have a vector (structures) in a struct (instances). I make a declaration of this struct called instance. The vector is a 3-layer vector of pointers, like so:
vector < vector < vector<scene::IAnimatedMeshSceneNode*> > > structures; (The type is from Irrlicht 3D). I have 3 nested "for" loops which looks similar to the following:
for (int a = 0; a < instance.structures.size(); a++) { /*note:vector size previously set*/
for (int b = 0; b < instance.structures[a].size(); b++){
for (int c = 0; c < instance.structures[a][b].size(); c++) {
if (1) { //checking value of variable not included in snippet
(instance.structures)[a][b][c] = smgr->addAnimatedMeshSceneNode(fl);
(instance.structures)[a][b][c]->setPosition(renderPos);
}
}
}
}
The problem is in these two lines, I think:
(instance.structures)[a][b][c] = smgr->addAnimatedMeshSceneNode(fl);
(instance.structures)[a][b][c]->setPosition(renderPos);
These are currently referencing the pointers, it seems. The program compiles but crashes at this point. I need them to reference the values of the pointers. Problem is, I don't know where to put the dereference operator (*). Where should it go?
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Apr 29, 2013
I'm trying to write a function that takes two linked lists and creates a third one with only the common elements.
It assumes the first list (the caller) has no dups, but it doesn't seem to be working. The program doesn't crash, it just hangs when it is supposed to display L3 (the third list)..everything else runs and is displayed fine.
template <typename T>
LList <T> LList <T>:: common (LList <T> &B)//common fct
{
Node <T> *hunter1 = Head;
[Code]......
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Jun 29, 2013
I have a linked list comprised of chars like so...
Code:
node1 - "p"
node2 - "o"
node3 - "p"
I need a function that will take in three perameters...node *replaceChar(node *head, char key, char *str)Stipulations of this function. head is the head of the list, 'key' and 'str' are guaranteed to contain alphanumeric characters only (A-Z, a-z, and 0-9). str can range from 1 to 1023 characters (inclusively). So if I call this function with these perameters..
Code:
node *head == /*the head of the list to be examined*/
char key == "p"char *str == "dog"The new list will look like this...
node1 - 'd'
node2 - 'o'
node3 - 'g'
node4 - 'o'
node5 - 'd'
node6 - 'o'
node7 - 'g'
All instances of 'p' were replaced with 'dog' I have a toString function which takes in a string and converts it to a linked list and returns the head. So assume that you can call the function on str = "dog" so...
Code:
toString(str) == /*this will return the head to the list made from the str*/
If it's unclear what my question is...I am stumped on how to write the replaceChar function the one that takes in three perameters..
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Dec 31, 2014
Code:
// Write a function called insertEntry() to insert a new entry into a linked list.
Have the procedure take as arguments a pointer to the list entry to be inserted (of type struct entry as defined in this chapter), and a pointer to an element in the list after which the new entry is to be inserted.
// The function dveloped in exercise 2 only inserts an element after an existing element in the list, thereby prenting you from inserting a new entry at the front of the list.
(Hint: Think about setting up a special structure to point to the beginning of the list.)
#include <stdio.h
struct entry1 {
int value;
struct entry1 *next;
};
[code]...
This is a working version of the exercise, but I don't think I'm doing what's asked. I was able to add an element to the beginning of the list using an if statement, not creating a special structure that points to the beginning of the list. How would I go about creating a special structure that points to the beginning of the list to add a new element at the beginning of the list?
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Aug 8, 2013
I am having some trouble getting a 3d array of pointers to link up with a linked list for each of the array elements. the 3d array of pointers is declared like this:
Code:
struct particle *cell[MAXCELLS][MAXCELLS][MAXCELLS]; and there are linked lists declared like this:
Code: struct particle { /* structure for particles */
double sw[3]; /* square well components */
double hs[3]; /* hard sphere components */
double u[3]; /* unit vector for rotations */
struct particle *link;
};
I want to get the array pointers 'cell[x][y][z]' to point to the first observed particle in a function next to main, something like this:
Code:
void generate_list(){
int i,j,k,l;
/* determine the number of cells to decompose the simulation box in each of x, y and z directions*/
int(cells_x) = floor(boxX/cell_size);
int(cells_y) = floor(boxY/cell_size);
int(cells_z) = floor(boxZ/cell_size);
/* initialise the array of pointers to NULL */
for (j=0;j<cells_x;j++){
[Code]...
I am getting a pointer type cast error when I compile "assignment from incompatible pointer type",
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Dec 27, 2012
I am studying/writing/ code for a future Advanced Data Structure class in C++; however I am not suppose to use STL, Templates and etc (the way I just code "kinda" of resembles what I have to use).
My application is suppose to read/analyze all integers contained in a text file of 5-digit integers (10000 - 99999).
For simplicity I am using the following input (or check the attached):
20007 20008 20009
20010 20010
20012 20012
20013
20014 20010
20015
20016 ....
So far, my code is not displaying/printing the lists separated by the first digit of these 5-digits integers. I am expecting it to display/print logically/similar to the following:
Output:
Results for input file numbers.txt:
27 total integers read from file
The 3 unique integers beginning with digit 1 were
18399 17342 19948
The 6 unique integers beginning with digit 3 were
39485 34710 31298 38221 35893 32791
The 4 unique integers beginning with digit 4 were
43928 49238 45678 43210
The 6 unique integers beginning with digit 6 were
64545 62987 66221 61777 66666 65432
The 2 unique integers beginning with digit 8 were
88888 86861
The 1 unique integer beginning with digit 9 was
98765
There were 22 unique 5-digit integers in the file.
The highest unique count in one list was 6 integers.
My code that will follow soon displays/prints only the LAST 5-digits "group" of integers (in this case the 5-digits starting with 3). I am not sure what's wrong with my code; perhaps I am not designing it correctly. May be my calls in it are on the wrong place or I have to write all integers and then traverse it and output it (if that's the case, I am not sure how).
My code follows:
#include <iostream>
#include <fstream>
#include <iomanip>
using namespace std;
const int MAX_CELLS = 10;
const int UNIQUE_FIVE_DIGIT = 5;
[Code] .....
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Feb 16, 2014
I have a the following in a header file.
Code:
struct SortedList{
void * data;
struct SortedList * next;
struct SortedList * previous;
int (*compareFunc)(void *, void *);
void (*destructor)(void *);
[Code] ....
In a .c file, I implemented the SLCreate function.
Code:
SortedListPtr SLCreate(CompareFuncT cf, DestructFuncT df){
struct SortedList item;
item.data = NULL;
item.next = (struct SortedList *) malloc(sizeof(struct SortedList));
[Code] ....
In main.c, I try to do the following:
Code:
SortedListPtr list = SLCreate(&compareInts, &destroy);
A bunch other code that does not alter list or it's contents at all.
struct SortedList item = (*list);
void * data = item.data;
if (data != NULL) {
printf(Why did data become not null???
"); }
How come my variable data became not null anymore when I haven't altered it at all....
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Feb 13, 2013
I am an IT student currently learning linked list. I have a problem with my code here. After I call addFront() my list doesn't change when I display it. How do I somewhat change/fill my list without changing the function type? I know it works on pointers still messed up with linked list.
Code:
typedef struct node *nodeptr;
struct node{int item;
nodeptr next;};
typedef nodeptr List;
}
[code]....
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May 30, 2013
I'm working on a linked list and was wondering how this looks to everybody else for a deleteList function.
void deleteList(Node* head)
{
Node* iterator = head;
while (iterator != 0)
[code].....
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Feb 26, 2013
Having some frustrating issues trying to free memory from a dynamically allocated array of pointers to linked lists. I think the problem is in how I initialize the pointers to NULL. Is there a more elegant way to have the program recognize that the list is empty so it knows to create a head node for the linked list in the function 'add_end_stub_to_array'?
I ran the code through Valgrind and it says that memory is definitely lost from this array.
This is the structure definition.
Code: struct stub_edge {
int loc_id;
int anim_type;
int mkt;
struct stub_edge *next_node;
};
Here is the code snippet from main allocating and deallocating memory to the array.
Code:
struct stub_edge **stub_list = (struct stub_edge **)malloc( sizeof(struct stub_edge *) * 12);
for (i = 0; i < 12; i++)
{
stub_list[i] = (struct stub_edge *)malloc(sizeof(struct stub_edge));
stub_list[i] = NULL;
}
stub_list = add_end_stub_to_array(end_stubs, stub_list);
destroy_end_stub_array(stub_list);
Here the function for adding nodes to the lists by reading through a dynamically allocated 2D array. (The end_stubs array is ordered by month and each linked list represents events occuring within the month).
Code:
struct stub_edge **add_end_stub_to_array(int **end_stubs, struct stub_edge **list)
{
long int i = 0;
int mon = 0;
struct stub_edge *current_node1;
struct stub_edge *new_node1;
int break1 = 0;
while(i < num_edges && break1 == 0 && mon < 12)
[Code]...
Here is the function for freeing memory from the list.
Code:
void destroy_end_stub_array(struct stub_edge **list)
{
if(list != NULL)
{
int mon = 0;
struct stub_edge *current_node1;
struct stub_edge *new_node1;
for(mon = 0; mon < 12; mon++)
[Code]...
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Apr 14, 2014
I have a data structure defined up here called this:
typedef list <classSpec*> ClassSpecList;
I'm trying to add stuff into the list here based on functions that return certain values of that match the same data type. In one function, I have a list pointer object defined here and I have another statement that calls a function.
ClassSpecList *answer = 0;
classSpec *thisanswer = parseClass(br);
Basically I'm trying to add the results of what thisanswer returns into my main ClassSpecList. Problem is, when I try
answer->push_back(new classSpec (*thisanswer));
It compiles but I get a seg fault
When I try somethign else like:
answer->insert(ClassSpecList.begin(), *thisanswer);
I keep getting primary expression errors and I do not know why. I even tried it with other list made without typedef and I still get those.
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Jun 25, 2014
I need to create a list of all members of a struct using the sturct definition as input. The struct is NOT part of the program, but is the input to the program.
The struct that I am using changes over time as features are added. I need the complete, fully qualified field names to then generate a table with all names with their offsets, type and length.
This information then allows me to create readers of the data that will run on different architectures, compilers and operating systems.
The struct currently has 800+ lines and uses typedef and embedded structs.
Perhaps this could be done creating LEX, YACC, Perl, SED, AWK or other language system.
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Apr 22, 2014
I am writing a class that dynamically allocates an array that holds a user-defined number of test scores (test scores go from 0 to 10 both included). Once all the test scores are entered and validated (values only between 0 and 10, both included), the array should be passed to a function that sorts them in ascending order. Another function should be called that calculates theaverage of all the scores.The main program should display the sorted list of scores and the average of the scores with appropriate headings.
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May 15, 2013
I need to make the functions using these function prototypes. I am mainly having problems with GetFirst() and SwapData() but how to do it..
Header File with Prototypes
Code:
#ifndef LINKEDLIST_H
#define LINKEDLIST_H
/**
* @file
* This file provided a doubly-linked list implementation capable of storing any arbitrary data.
* The list implementation relies on a chain metaphor: a list is merely a sequence of links
* (ListItems) and there is no separate construct to represent the entire list, each ListItem in it
[Code]....
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May 7, 2013
I read an article on linked list here: C Linked List Data Structure Explained with an Example C Program
Code:
struct test_struct* search_in_list(int val, struct test_struct **prev)
{
struct test_struct *ptr = head;
struct test_struct *tmp = NULL;
bool found = false;
}
[code].....
What is "if(prev)"? Wouldn't "prev" always have the same value? Secondly, if tmp is NULL (which will be the case when the loop if(ptr->val == val) finds a match the first time it is run), is *prev assigned a NULL?
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Jan 2, 2014
I'm having a small issue here with my linked list.I built a linked list with strings and it worked perfectly.Now since i'm using strtok() to separate the string.for now here's what i've got:
Code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct dict_word *word;
typedef struct node *Node;
typedef struct double_linked_list *DLL;
}
[code]....
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