get the last adress of queue node.

#include <iostream>
#include <stdlib.h>

struct qnode {
    int value;
    qnode* next;
    qnode() {
        next = NULL;
    }
};

void insertNode(qnode*& ntop, qnode* newNode) {
    if(ntop == NULL) {
        ntop = newNode;
    } else {
        newNode->next = ntop;
        ntop = newNode;
    }
}

void npop(qnode*& ntop) {
    if (ntop == NULL) {
        exit(0);
    }
    qnode** last = &ntop;
    while((*last) != NULL) {
        last = &((*last)->next);
    }

    last = NULL;
    /*
    if(ntop->next == NULL) {
        ntop = NULL;
    } else {
        npop(ntop->next);
    }*/
}

void nvisit(qnode* ntop) {
    if(ntop == NULL) {
        std::cout<<"end.";
    } else {
        std::cout<<ntop->value<<"->";
        nvisit(ntop->next);
    }
}

int main() {
    qnode* mquque = new qnode;
    mquque->value = 12;
    qnode* n1 = new qnode;
    qnode* saved = mquque;
    n1->value = 21;
    insertNode(mquque, n1);
    npop(mquque);
    nvisit(mquque);
    delete saved;
    delete n1;

    return 0;
}