Thread: Rusty with c++ need some help with errors involving pointers and stuff

Bit rusty with C++ and not sure how to fix these errors i'm getting. Any help is much appreciated!!!

Here's the errors:

DFS.cpp: In function 'void DFS(Node*)':
DFS.cpp:64: error: cannot convert 'Node' to 'Node*' for argument '1' to 'void DFS_Visit(Node*)'
DFS.cpp: In function 'Node* makeGraph()':
DFS.cpp:130: error: no match for 'operator*' in '**(((Node*)(((long unsigned int)i) * 16ul)) + graph)'
DFS.cpp: In function 'Node* makeSample()':
DFS.cpp:150: error: no match for 'operator=' in '*(((Node*)(((long unsigned int)i) * 16ul)) + graph) = 0l'
DFS.cpp:15: note: candidates are: Node& Node:: operator=(const Node&)
DFS.cpp:158: error: name lookup of 'i' changed for new ISO 'for' scoping
DFS.cpp:148: error: using obsolete binding at 'i'



And here's the code:

Code:

#include <iostream>
#include <iomanip>
#include <cstdlib>

using namespace std;


int operationsCounter=0;
int ntime=0, verts, edges;
string* color = new string[1];
int* pi = new int[1];
int* d = new int[1];
int* f = new int[1];

struct Node{
  int data;
  Node* next;
};
void InsertAfter(Node *head, int value){
  if(head==NULL){
    Node* temp=NULL;
    temp = new Node;
    temp->data = value;
    temp->next = NULL;
    head = temp;
  }else{
    Node *temp = new Node;
    temp->data = value;
    temp->next = (head)->next;
    (head)->next = temp;
  }
}


void DFS_Visit(Node* u)
{
  color[u->data]="gray";
  d[u->data]=(++ntime);
  int v=u->data;
  while((u=u->next)!=NULL)
  {
    if (color[u->data]=="white")
    {
      pi[u->data]=v;
      DFS_Visit(u);
    }
  }
  color[v]="black";
  f[v]=(++ntime);
}

void DFS(Node* G)
{
  for (int u=0; u<verts; u++)
  {
    color[u]="white";
    pi[u]=-1;
  }
  ntime=0;
  for (int u=0; u<verts; u++)
  {
    if (color[u]=="white")
    {
      DFS_Visit(G[u]);
    }
  }
}

void printResults()
{
  cout << "       d    f    pi " << endl;
  for (int i=0; i<verts; i++)
  {
    if(i<10)
      cout << "    " << i;
    else if(i<100)
      cout << "   " << i;
    else if(i<1000)
      cout << "  " << i;
    else
      cout << " " << i;
    if(d[i]<10)
      cout << "    " << d[i];
    else if(d[i]<100)
      cout << "   " << d[i];
    else if(d[i]<1000)
      cout << "  " << d[i];
    else
      cout << " " << d[i];
    if(f[i]<10)
      cout << "    " << f[i];
    else if(f[i]<100)
      cout << "   " << f[i];
    else if(f[i]<1000)
      cout << "  " << f[i];
    else
      cout << " " << f[i];
    if(pi[i]<10)
      cout << "    " << pi[i] << endl;
    else if(pi[i]<100)
      cout << "   " << pi[i] << endl;
    else if(pi[i]<1000)
      cout << "  " << pi[i] << endl;
    else
      cout << " " << pi[i] << endl;
    
  }
  cout << endl << endl; 
  cout << "Number of operation: " << operationsCounter << endl;
}

bool alreadyInList(Node* llist, int data)
{
  if(llist==NULL)
    return false;
  else if(data==llist->data)
    return true;
  else
    return alreadyInList(llist->next, data);
}

Node* makeGraph()
{
  int u, v;
  u=0;
  v=0;
  Node* graph = new Node[5];
  for(int i=0; i<5; i++)
  {
    &graph[i]=NULL;
    InsertAfter(&graph[i], i);
  }
  for(int i=0; i<edges; i++)
  {
    while(alreadyInList(&graph[u], v))
    {
      u = rand() % verts;
      v = rand() % verts;
    }
    InsertAfter(&graph[u], v);
  }
  return graph;
}

Node* makeSample()
{
  Node* graph = new Node[5];
  for(int i=0; i<verts; i++)
  {
    graph[i]=NULL;
    InsertAfter(&graph[i], i);
  }
  InsertAfter(&graph[0], 1);
  InsertAfter(&graph[1], 2);
  InsertAfter(&graph[1], 3);
  InsertAfter(&graph[2], 3);
  InsertAfter(&graph[2], 4);
  InsertAfter(&graph[4], i);
  return graph;
}

int main()
{
  int option;
  while (option!=3)
  {
    cout << "Please select an option: " << endl;
    cout << "1) Run DFS on the sample graph" << endl;
    cout << "2) Run DFS on a customized random graph" << endl;
    cout << "3) Exit" << endl;
    cin >> option;
    if(option==1)
    {
      verts=5;
      edges=6;
	  color = new string[verts];
      pi = new int[verts];
      d = new int[verts];
      f = new int[verts];
      operationsCounter=0;
      DFS(makeSample());
      printResults();
    }
    if(option==2)
    {
      cout << "How many vertices would you like the graph to have?" << endl;
      cin >> verts;
      cout << "How many edges would you like the graph to have?" << endl;
      cin >> edges;
	  color = new string[verts];
      pi = new int[verts];
      d = new int[verts];
      f = new int[verts];
      operationsCounter=0;
      DFS(makeGraph());
      printResults();
    }
  }
  cout << "Thank you.  Goodbye!";
  return 0;
}

For

DFS.cpp: In function 'void DFS(Node*)':
DFS.cpp:64: error: cannot convert 'Node' to 'Node*' for argument '1' to 'void DFS_Visit(Node*)'

change

Code:

DFS_Visit(G[u]);

to:

Code:

DFS_Visit( &G[u] );

For

DFS.cpp:150: error: no match for 'operator=' in '*(((Node*)(((long unsigned int)i) * 16ul)) + graph) = 0l'
DFS.cpp:15: note: candidates are: Node& Node:: operator=(const Node&)

try changing

Code:

graph[i]=NULL;

to:

Code:

&graph[i]=NULL;

For

DFS.cpp:158: error: name lookup of 'i' changed for new ISO 'for' scoping
DFS.cpp:148: error: using obsolete binding at 'i'

Move the int i = 0; out before the for loop in:

Code:

for(int i=0; i<verts; i++)

Ah thanks! But

Code:

&graph[i]=NULL;

still gives the error:

DFS.cpp: In function 'Node* makeGraph()':
DFS.cpp:130: error: invalid lvalue in assignment

Yes, I want it to be an array of pointers (Nodes)..... How do I do that then?

How did the OP post this syntax highlighted C++ code?
Is it automatically enabled now, i think i need to post some code to test it!

http://dwks.theprogrammingsite.com/myprogs/cfonline.htm

u->data is causing a seg fault...... why?

in particular the first time i think it is used is in (where i know it is causing the seg fault)

color[u->data]="gray";

in DFS_Visit

any thoughts?

Code:

template <typename Unknown>
class Shahrukh : public FilmStar {

    int i;
    float f;

public:
    void dance();
    void act();
    long double earn();
};

Originally Posted by laserlight

You could write:

• Why do you use global variables in your code?
• Why do you give your variables such undescriptive names as pi, d and f?
• Where is your delete[] to match your new[]?
• Where is your delete to match your new?
• In main, why do you use option before it is initialised?

-multiple functions modifying them, so only way I know
-hw assignment and thats what they said to use, lol, its for an algorithms class so they know what they are supposed to be (pi=parent, d=discovered time, f=finished time)
-don't have one.... don't really need it
-just initialized it to 0 to begin with

i have extra couts in there to find the seg fault so you can just ignore them....

Code:

#include <iostream>
#include <iomanip>
#include <cstdlib>

using namespace std;


int operationsCounter=0;
int ntime=0, verts, edges;
string* color = new string[1];
int* pi = new int[1];
int* d = new int[1];
int* f = new int[1];

struct Node{
  int data;
  Node* next;
};
void InsertAfter(Node *head, int value){
  if(head==NULL){
    Node* temp=NULL;
    temp = new Node;
    temp->data = value;
    temp->next = NULL;
    head = temp;
  }else{
    Node *temp = new Node;
    temp->data = value;
    temp->next = (head)->next;
    (head)->next = temp;
  }
}


void DFS_Visit(Node* u)
{
	cout << "---in DFS_Visit u=" << endl;
	cout << "---" << &u->data << endl;
  color[u->data]="gray";
  cout << "---color" << endl;
  d[u->data]=(++ntime);
  cout << "---d" << endl;
  int v=u->data;
  cout << "---DFS_Visit before while" << endl;
  while((u=u->next)!=NULL)
  {
	  cout << "---DFS_Visit in while u=" << u->data << endl;
    if (color[u->data]=="white")
    {
      pi[u->data]=v;
      DFS_Visit(u);
    }
  }
  cout << "---DFS_Visit after while" << endl;
  color[v]="black";
  f[v]=(++ntime);
}

void DFS(Node** G)
{
  for (int u=0; u<verts; u++)
  {
    color[u]="white";
    pi[u]=-1;
  }
  ntime=0;
  cout << "---DFS 1" << endl;
  for (int u=0; u<verts; u++)
  {
    if (color[u]=="white")
    {
      DFS_Visit(G[u]);
    }
  }
  cout << "---DFS 2 done" << endl;
}

void printResults()
{
  cout << "       d    f    pi " << endl;
  for (int i=0; i<verts; i++)
  {
    if(i<10)
      cout << "    " << i;
    else if(i<100)
      cout << "   " << i;
    else if(i<1000)
      cout << "  " << i;
    else
      cout << " " << i;
    if(d[i]<10)
      cout << "    " << d[i];
    else if(d[i]<100)
      cout << "   " << d[i];
    else if(d[i]<1000)
      cout << "  " << d[i];
    else
      cout << " " << d[i];
    if(f[i]<10)
      cout << "    " << f[i];
    else if(f[i]<100)
      cout << "   " << f[i];
    else if(f[i]<1000)
      cout << "  " << f[i];
    else
      cout << " " << f[i];
    if(pi[i]<10)
      cout << "    " << pi[i] << endl;
    else if(pi[i]<100)
      cout << "   " << pi[i] << endl;
    else if(pi[i]<1000)
      cout << "  " << pi[i] << endl;
    else
      cout << " " << pi[i] << endl;
    
  }
  cout << endl << endl; 
  cout << "Number of operation: " << operationsCounter << endl;
}

bool alreadyInList(Node* llist, int data)
{
	cout << "---already in list" << endl;
  if(llist==NULL)
    return false;
  else if(data==llist->data)
    return true;
  else
    return alreadyInList(llist->next, data);
}

Node** makeGraph()
{
  int u, v;
  u=0;
  v=0;
  Node** graph = new Node*[5];
  for(int i=0; i<5; i++)
  {
    graph[i]=NULL;
    InsertAfter(graph[i], i);
  }
  for(int i=0; i<edges; i++)
  {
    while(alreadyInList(graph[u], v))
    {
      u = rand() &#37; verts;
      v = rand() % verts;
    }
    InsertAfter(graph[u], v);
  }
  return graph;
}

Node** makeSample()
{
  Node** graph = new Node*[5];
  int i=0;
  while(i<verts)
  {
    graph[i]=NULL;
    InsertAfter(graph[i], i);
	i++;
  }
  InsertAfter(graph[0], 1);
  InsertAfter(graph[1], 2);
  InsertAfter(graph[1], 3);
  InsertAfter(graph[2], 3);
  InsertAfter(graph[2], 4);
  InsertAfter(graph[4], i);
  cout << "---Sample graph made ..........es." << endl;
  return graph;
}

int main()
{
  int option=0;
  while (option!=3)
  {
    cout << "Please select an option: " << endl;
    cout << "1) Run DFS on the sample graph" << endl;
    cout << "2) Run DFS on a customized random graph" << endl;
    cout << "3) Exit" << endl;
    cin >> option;
    if(option==1)
    {
      verts=5;
      edges=6;
	  color = new string[verts];
      pi = new int[verts];
      d = new int[verts];
      f = new int[verts];
      operationsCounter=0;
      DFS(makeSample());
      printResults();
    }
    if(option==2)
    {
      cout << "How many vertices would you like the graph to have?" << endl;
      cin >> verts;
      cout << "How many edges would you like the graph to have?" << endl;
      cin >> edges;
	  color = new string[verts];
      pi = new int[verts];
      d = new int[verts];
      f = new int[verts];
      operationsCounter=0;
      DFS(makeGraph());
      printResults();
    }
  }
  cout << "Thank you.  Goodbye!";
  return 0;
}

- thats just ugly and more work than required and since its now almost 2 a.m. and i'm running on 2 hours of sleep definately feeling lazy :-P
- actually the assignment description says to call them that.... sure i doubt i'd lose points if i did use something else, but i've also got this algorithm memorized with pi, d, and f so works for me
-doesn't matter for this class...
-int option=0;
while (option!=3)
nope looks initialized before use to me :-P

but as for the seg fault.... what wrong with color[u->data]="gray";