Question

I’m having a problem with my insertion on linked list. Here is my code:

    for(j = 0; j < SIZE; j++) {
        body = (textFile*) malloc (sizeof(textFile));
        body->word = words[index[j]];
        if(head == NULL) {
            head = tail = body;
        }
        else {
            tail->next = body;
            tail = body;   
            cout << tail->word << endl;
        }
    }

What hapens here is that the program crashes after it displays the 15th element on my linked list… I don’t know why. index is declared as index[20] = {0}; and SIZE is defined as 20, so the linked list is supposed to contain all 20 words inside words array. What can be its possbile cause? Could it be memory allocation? Thanks in advance 🙂

Heres more of my code. Sorry I’m a little ashamed to post it I’m not good in code elegance. Pardon.

    #include <iostream>
    #include <fstream>
    #include <string>
    #include <ctime>
    #include <cstdlib>
    #define SIZE 20

    using namespace std;

    struct textFile {
        string word;
        struct textFile *next;
    };

    textFile *head, *body, *tail, *temp;

    int main() {
        ifstream wordFile("WORDS.txt", ios::in); // file object constructor
        /* stores words in the file into an array */
        string words[SIZE];
        char pointer;
        int i;
        for(i = 0; i < SIZE; i++) {
            while(wordFile >> pointer) {
                if(!isalpha(pointer)) {
                    pointer++;
                    break;
                }
                words[i] = words[i] + pointer;
            }
        }
        /* stores the words in the array to a randomized linked list */
        srand(time(NULL));
        int index[SIZE] = {0}; // temporary array of index that will contain         randomized indexes of array words
        int j = 0, ctr;
        // assigns indexes to array index
        while(j < SIZE) {
            i = rand() % SIZE;
            ctr = 0;
            for(int k = 0; k < SIZE; k++) {
                if(!i)
                    break;
                else if(i == index[k]) { // checks if the random number has         previously been stored as index
                    ctr = 1;
                    break;
                }
            }
            if(!ctr) {
                index[j] = i; // assigns the random number to the current         index of array index
                j++;
            }
        }
        /* makes sure that there are no double zeros on the array */
        ctr = 0;
        for(i = 0; i < SIZE; i++) {
            if(!index[i])
                ctr++;
        }
        if(ctr > 1) {
            int temp[ctr-1];
            for(j = 0; j < ctr-1; j++) {
                for(i = 0; i < SIZE; i++) {
                    if(!index[i]) {
                        int ctr2 = 0;
                        for(int k = 0; k < ctr-1; k++) {
                            if(i == temp[k])
                                ctr2 = 1;
                        }
                        if(!ctr2)
                            temp[j] = i;
                    }
                }
            }
            j = ctr - 1;
            while(j > 0) {
                i = rand() % SIZE;
                ctr = 0;
                for(int k = 0; k < SIZE; k++) {
                    if(!i || i == index[k]) {
                        ctr = 1;
                        break;
                    }
                }
                if(!ctr) {
                    index[temp[j-1]] = i;
                    j--;
                }
            }
        }
        head = tail = body = temp = NULL;
        for(j = 0; j < SIZE; j++) {
            body = (textFile*) malloc (sizeof(textFile));
            body->word = words[index[j]];
            if(head == NULL) {
                head = tail = body;
            }
            else {
                tail->next = body;
                tail = body;
                cout << tail->word << endl;
            }
            }
            temp = head;
        while(temp != NULL) {
            cout << temp->word << endl;
            temp = temp->next;
        }
        return 0;
    }

Answer 1

The problem is with the way you are initializing the body struct:

body = (textFile*) malloc (sizeof(textFile));

The string doesn’t get initialized, causing the segmentation fault when you try to assign to it. You should use the C++ new keyword instead:

body = new textFile;

The new keyword will assign memory for the struct as well as any object references contained in it.

Also see here