Double stack linked list segmentation fault

2022-05-06 13:04 Linkachus 17 imported from Stackoverflow

So I've been asked to make a C++ program Double stack with linked list. I can't find any tutorial or example on Google, most of them use Array to do it. so I have to figure it out how to do this, and end up with Segmentation Fault output in the end, which I still have no idea which part of my code is wrong here

#include <iostream>
using namespace std;

struct Node{
    public:
    int data;
    Node *next;
    Node *prev;
};
Node *head = NULL;
Node *tail = NULL;
Node *del = NULL;

void push(Node **head_ref, int data){
    Node *temp = new Node;
    temp->data = data;
    temp->next = head;
    head->prev = temp;
    head = temp;
}

void push2(Node **head_ref, int data){
    Node *temp = new Node;
    temp->data = data;
    tail->next = temp;
    temp->prev = tail;
    tail = temp;
}

void pop(Node **head_ref, int data){
    del = head;
    head->next->prev = NULL;
    head = del->next;
    del = NULL;
}

void pop2(Node **head_ref, int data){
    del = tail;
    tail->prev->next = NULL;
    tail = del->prev;
    del = NULL;
}

int peek(Node **head_ref){
    return head->data;
}

int main(){
    system("clear");
    push2(&head, 10);
}

any help is appreciated

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Can anyone pls tell me whats wrong with my code ? im stuck for the last 3 hours ,this question is bipartite graph in c++

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bool isBipartite(vector<int> graph[],int V)
{
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    vector<int> color(V,-1);
    
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I have a stat struct, and I'm looking for a way to get data out of it to be manipulated. The program will successfully run and print the desired st_mtime value, but including either of the "seg-fault" lines below causes a segmentation fault in runtime.
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I've had a hard time finding any examples of the usage of stat() that do anything other than print its contents, which makes me wonder if it's even possible.

So my question is, if it is possible, what am I missing?

P.S. I do wish to keep st_mtime in the Unix timestamp format to make it easier to manipulate.

Edit: After realizing that st_mtime is itself its own struct (timespec), how can I access the st_mtime.tv_sec member?

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compiler error

Segmentation Fault - unordered_map(tarjan's algorithm)

I have implemented Tarjan's algorithm to find strongly connected component in a graph and getting Segmentation fault for some large input.

#include <iostream>
#include <sstream>
#include <vector>
#include <stack>
#include <unordered_set>
#include <unordered_map>

using namespace std;

class Graph {
public:
    int n, m;
    unordered_map<int, unordered_set<int>> graph;

    Graph(int n, int m): n(n), m(m) {}

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        graph[u].insert(v);
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        for(const int& ch: graph[u]) {
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                scc_helper(ch, disc, low, st, inStack, scc, time);
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            } else if(inStack[ch]) {
                low[u] = min(low[u], disc[ch]);
            }
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        if(disc[u] == low[u]) {
            scc.push_back(unordered_set<int>());
            while(st.top() != u) {
                scc.back().insert(st.top());
                inStack[st.top()] = false;
                st.pop();
            }
            scc.back().insert(st.top());
            inStack[st.top()] = false;
            st.pop();
        }
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    vector<unordered_set<int>> get_scc() {
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            if(disc[p.first] == 0) 
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        } 
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        return scc;
    }
};

void read(string& input) {
    do {
        getline(cin, input);
    } while(input.length() > 0 && input[0] == '%');
}

Graph read_graph() {
    string input;
    istringstream ss;
    int n, m, v;

    read(input); ss.str(input);
    ss >> n >> m;
    ss.clear();

    Graph G(n, m);

    for(int u=1; u<=n; u++) {
        read(input); ss.str(input);
        while(ss >> v) {
            G.add_edge(u, v);
        } ss.clear();
        if(G.graph.find(u) == G.graph.end()) G.graph[u] = unordered_set<int>();
    }
    return G;
}

int main() {
    Graph G = read_graph();
    cerr << "read input\n";
    vector<unordered_set<int>> scc = G.get_scc();

    cout << scc.size() << "\n";
}

After debugging, I have found that the condition if(disc[u] == low[u]) is not getting evaluated to true when program throws segmentation fault. Another thing is that, Segmentation fault was received on lines disc[u] = low[u] = time++;, st.push(u); and inStack[u] = true; and at that time there were approx. 20,000 entries in each of the unordered_map and in stack.

Some details about input: for, n=16384 m=283794, the program is working correctly but for, n=58960 m=269439, it is throwing segmentation fault.

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Double stack linked list segmentation fault

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