When I run this code on VScode, it shows "test.c has stopped working". I was trying to Practice merge sort

Question

C/C++

I'm using VScode. When I run this program file stopped immediately.

I have encountered this kind of problem before. but it happened because I scanned an array without '&' addressing it.

but this time I couldn't find the problem.

this function will print an array.

    #include <stdio.h>
    void print_array ( int size, int data[], char *str) // this function will print array.
    {
        int i;
        printf("%s", str);
    
        for (i = 0; i < size; i++)
        {
            printf("%d\t", data[i]);
        }
    }

This function will take two sorted arrays, merge-sort them and it will give a sorted array.

    void merge(int a[], int b[], int c[], int x, int y) //this function will merge-sort two sorted arrays.
    {
        int i = 0, j = 0, k = 0;
        
        while ( i < x && j < y)
        {
            if (a[i] < b[j])
            {
                c[k++] = a[i++];
            }
            else
                c[k++] = b[j++];
        }
        while (i < x)
        {
            c[k++] = a[i++];
        }   
        while(j < y)
        {
            c[k++] = b[j++];
        }
    }

This main function will take the array's elements, and perform all task defined in the above functions

I think the problem is in the int main() function. Because the problem doesn't start to run at all.

    int main (void)
    {
        int x, y, i, j;
        int a[x];
        int b[y];
        int c[x+y];
        printf("Enter size of first array: ");
        scanf("%d", &x);
        printf("\nEnter sorted elements of first array:\n");
        for(i = 0; i < x; i++)
        {
            scanf("%d", &a[i]);  //it will take elements of array. 
        }
        print_array( x, a, "\nFirst array\n"); //print the first array.
        printf("\n\n");
    
        printf("Enter size of second array: ");
        scanf("%d", &y);
        printf("\nEnter sorted elements of Second array:\n");
        for(j = 0; j < y; j++)
        {
            scanf("%d", &b[i]);
        }
        print_array( y, b, "\nSecond array\n"); //print second array.
        printf("\n\n");
    
        merge(a, b, c, x, y); /merge sort
    
        print_array( x+y, c, "\nSorted Data\n"); //print sorted data
        printf("\n\n");
    
        return 0;
    
    }

Answer 1

What are you actually trying to implement? If you are trying to implement Merge sort algorithm, this is not the way to implement Merge sort.

Your question is vague. You did not specify whether you got a runtime error or compile time error.

If you Copied your code correctly, I think you are getting a compilation error because a comment is missing /. Fix the comment. Edit the line merge(a, b, c, x, y); /merge sort to merge(a, b, c, x, y); //merge sort.

You may also get runtime error or undefined behavior because you declared three arraies int a[x], int b[y] & int c[x+y]; without initializing the values of x & y. One possible solution is initializing the values of x & y.

int main(void) {
    int x, y, i, j;
    printf("Enter size of first array: ");
    scanf("%d", &x);
    //declare array a[x] here 
    int a[x];
    printf("\nEnter sorted elements of first array:\n");
    for (i = 0; i < x; i++) {
        scanf("%d", &a[i]);  //it will take elements of array.
    }
    print_array(x, a, "\nFirst array\n"); //print the first array.
    printf("\n\n");

    printf("Enter size of second array: ");
    scanf("%d", &y);
    //declare array b[y] here 
    int b[y];
    printf("\nEnter sorted elements of Second array:\n");
    for (j = 0; j < y; j++) {
        scanf("%d", &b[i]);
    }
    print_array(y, b, "\nSecond array\n"); //print second array.
    printf("\n\n");

    //declare array c[x+y] here 
    int c[x + y];
    merge(a, b, c, x, y); //merge sort

    print_array(x + y, c, "\nSorted Data\n"); //print sorted data
    printf("\n\n");

    return 0;
}

Another solution of the last problem is to declare the array using a macro MAX, assuming that the values of x and y less than MAX. Caution: this process is mot memory efficient.

#define MAX 100000
int main(void) {
    int x, y, i, j;
    int a[MAX];
    int b[MAX];
    int c[MAX + MAX];
    .....
    .....
    .....
}