CODEWITHSUNDEEP
c++linked-list
fast tooth
fast tooth

Reputation: 2459

c++ linked list segfault debug

I am met a segfault during implementing my own linked_list in C++. I spent hours on it but still cannot figure out the bug. Any help will be appreciated. Thank you in advance.

I think the error is in find_kth1() function, but I don't know what i do wrong. I can print the linked list just as expected. 

/* 
 *
 * find kth to last element in a singly linked list
 */

#include <iostream>
// #include "../linked_list.h"
using namespace std; 

struct Node {
    int data ; 
    struct Node *next;
}; 

Node* push(Node *head, int d){ 
    // push to top
    Node *n = new Node; 
    n->data = d; 
    n->next = head;
    return n;
}


void print_LL( Node* head){ 
    Node* p = head;
    while(p) { 
        cout << p->data << ' '; 
        p = p->next; 
    }
} 

int find_length( Node* head) { 
    int len = 0; 
    Node* p = head; 
    while(p){
        len ++; 
        p = p->next;
    }
    return len;
}

Node* find_kth1( Node* head, int k){ 
    // find length, scan twice
    int len  = find_length(head);

    Node *p = head; 
    int i = 0;
    while( i < len-k){
        i ++ ;
        p = p->next;
    }
    return p;
}



int main( void){ 
    Node *head; 
    head = push( head, 2) ; 
    head = push( head, 3) ; 
    head = push( head, 4) ; 
    head = push( head, 5) ; 
    head = push( head, 2) ; 

    print_LL( head); 


    int k = 3;

    Node *p = find_kth1( head, k);

    // cout<<p->data<<endl;
}

Upvotes: 0

Views: 101

Answers (1)

radar
radar

Reputation: 13425

The head pointer need to be initialized

It is used with out initialization

Normally compiler gives warning , so always heed to the warnings

Node *head=NULL;

Upvotes: 4

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