alternate list, C++ (gcc)

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// 1. Given linked list as a-x-b-y-c-z
// output it as a-b-c-z-y-x
// that is reverse alternate element and append to end of list

#include <iostream>

using namespace std;

struct Node {
    int data;
    Node* next;
    Node(int d, Node* n): data(d), next(n) {}
};

Node* reverse(Node* node) {
    Node* prev = NULL;
    Node* cur = node;
    Node* next;

while (cur) {
        next = cur->next;
        cur->next = prev;
        prev = cur;
        
        cur = next;
    }
    return prev;
}

void alternate(Node* node) {
    Node* cur = node;
    Node* second = cur->next;
    
    Node* before;
    
    bool b = true;
    
    while (cur) {
     
        if (b)
            before = cur;
        b = !b;
        
        Node* firstNext = cur->next;
        Node* secondNext = NULL;
        if (firstNext)
            secondNext = firstNext->next;
        
        cur->next = secondNext;
        
        
        cur = firstNext;
    }
    
    before->next = reverse(second);
 
}

void print(Node* n) {
    while (n) {
        cout << n->data << " ";
        n = n->next;
    }
    cout << endl;
}

int main()
{
    Node* node = new Node(1, new Node(2, new Node(3, new Node(4, new Node(5, new Node(6, new Node(7, NULL)))))));
    
    print(node);
    alternate(node);
    print(node);

}

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Compilation time: 0.32 sec, absolute running time: 0.04 sec, cpu time: 0 sec, memory peak: 3 Mb, absolute service time: 0.36 sec