c++ - The first element of a ( custom ) doubly linked list is repeated -

-

i need make custom doubly linked list course of data structures.

but first element of list repeated , can't see error.

this push_back function :

template <class dt> void list<dt>::push_back(const dt& elem) {      if(first->back == nullptr && first->forward == nullptr) {          first->current = elem;           last->current = elem;         last->back = first;          first->forward = last;          return;     } else {           listobject<dt> *temp = new listobject<dt>(*last);          last = new listobject<dt>(); last->back = temp; last->forward = nullptr; last->current = elem;         temp->back->forward = temp;         temp->forward = last;      }  }

the main

list<int> c;      c.push_back(66);     c.push_back(44);     c.push_back(88);     c.push_back(58);      std::cout << "---------------------------" << std::endl;     for(listobject<int> *a = c.first; a; = a->forward) {          std::cout << a->current << std::endl;     }

edited here listobject class

template <class ldt> class listobject {  public :      listobject* back;     ldt current;     listobject* forward;      listobject(const ldt& elem, listobject&  _back, listobject& _forward) {          = &_back;         current = elem;         forward = &_forward;       }      listobject() {         = nullptr;         forward = nullptr;     }      listobject(const listobject& lista) {          = lista.back;         current = lista.current;         forward = lista.forward;     }      ~listobject() {          delete back;         delete forward;         current;     }      listobject<ldt> makelist(const ldt& elem, listobject&  _back, listobject& _forward) {          return  listobject<ldt>::listobject(elem, _back, _forward);     }      void assing(ldt elem) {          current = elem;      }      bool hasforward() {          if(forward != nullptr) {return true;} else{return false;}     }    };

modify else clause :

listobject<dt> *temp = last;  last = new listobject<dt>(); last->back = temp; last->forward = nullptr; last->current = elem; temp->forward = last;

this fix memory leak.

replace if clause :

if(first == nullptr) { //list empty          first = new listobject();         first->current = elem;          first->back = nullptr;         first->forward = nullptr;          last = first; //last first, not duplicate          return; }

this fix duplicated first element.


Comments

Post a Comment

Popular posts from this blog

java - activate/deactivate sonar maven plugin by profile? -

-
i use sonar plugin executes if activated in maven profile. sonar runs on every compile. the problem build fail other team members not have sonar application installed locally. pom.xml checked in team members same copy including sonar configuration, don't want them modify purpose of disabling sonar (they might inadvertently check modified copy in). please advise how configure maven (.m2/settings.xml) and/or pom.xml sonar feature can enabled/disabled local profile. here sonar configuration in each project's pom.xml: <plugin> <groupid>org.codehaus.mojo</groupid> <artifactid>sonar-maven-plugin</artifactid> <version>1.0</version> <executions> <execution> <id>make-sonar</id> <phase>compile</phase> <goals> <goal>sonar</goal> </goals> </execution> </executions> ...
Read more

python - TypeError: can only concatenate tuple (not "float") to tuple -

-
i'm new python, question might easy, anyway, patience: as trying call newton-raphson method calculate implied volatility in black-scholes formula call/put option pricing, first thing is, newton method in scipy.optimize seems calculate function's zeros, in black-scholes formula, want function's value option price, not zero. (i'm new here programming, i'm not sure techniques.) should write function things like: def f(sigma, price): return bsformula(s0,k,r,t,q,sigma) - price then, while calling newton method, takes args=() 1 parameter in function, write this: value = newton(bsprice2, 0.5, args=price) but error message: file "bs.py", line 36, in bsimpvol value = newton(bsprice2, 0.5, args=float(price)) file "/usr/lib/python2.7/dist-packages/scipy/optimize/zeros.py", line 143, in newton q0 = func(*((p0,) + args)) typeerror: can concatenate tuple (not "float") tuple could tell me why that? how fix it? apprecia...
Read more

java - What is the difference between String. and String.this. ? -

-
this question has answer here: meaning of .this , .class in java 2 answers i'll straight point. im still learning bit of syntax , want know difference between code is code a: public class buttonz extends jbutton{ public buttonz(){ settext(new string(string.valueof(i))); } } please ignore fact i undeclared, not lost. code b: public class buttonz extends jbutton{ public buttonz(){ settext(new string(string.this.charat(i))); } } what don't yet understand difference in typing string.this , string. i under assumption when use dot operator on class accessing it's static methods(and/or variables if they're not hidden). i have studied little bit , have concluded when using string. accessing string static methods.. when using string.this. i'm accessing methods class buttonz extendi...
Read more