C code to implement B Tree

//C program to implement B Tree //

#include<stdlib.h>
#include<stdio.h>
#define M 5

struct node{
    int n; /* n < M No. of keys in node will always less than order of B tree */
    int keys[M-1]; /*array of keys*/
    struct node *p[M];   /* (n+1 pointers will be in use) */
}*root=NULL;

enum KeyStatus { Duplicate,SearchFailure,Success,InsertIt,LessKeys };

void insert(int key);
void display(struct node *root,int);
void DelNode(int x);
void search(int x);
enum KeyStatus ins(struct node *r, int x, int* y, struct node** u);
int searchPos(int x,int *key_arr, int n);
enum KeyStatus del(struct node *r, int x);

int main()
{
    int key;
    int choice;
    printf("Creation of B tree for node %d\n",M);
    while(1)
    {
        printf("1.Insert\n");
        printf("2.Delete\n");
        printf("3.Search\n");
        printf("4.Display\n");
        printf("5.Quit\n");
        printf("Enter your choice : ");
        scanf("%d",&choice);

        switch(choice)
        {
            case 1:
                printf("Enter the key : ");
                scanf("%d",&key);
                insert(key);
                break;
            case 2:
                printf("Enter the key : ");
                scanf("%d",&key);
                DelNode(key);
                break;
            case 3:
                printf("Enter the key : ");
                scanf("%d",&key);
                search(key);
                break;
            case 4:
                printf("Btree is :\n");
                display(root,0);
                break;
            case 5:
                exit(1);
            default:
                printf("Wrong choice\n");
                break;
        }/*End of switch*/
    }/*End of while*/
    return 0;
}/*End of main()*/

void insert(int key)
{
    struct node *newnode;
    int upKey;
    enum KeyStatus value;
    value = ins(root, key, &upKey, &newnode);
    if (value == Duplicate)
        printf("Key already available\n");
    if (value == InsertIt)
    {
        struct node *uproot = root;
        root=malloc(sizeof(struct node));
        root->n = 1;
        root->keys[0] = upKey;
        root->p[0] = uproot;
        root->p[1] = newnode;
    }/*End of if */
}/*End of insert()*/

enum KeyStatus ins(struct node *ptr, int key, int *upKey,struct node **newnode)
{
    struct node *newPtr, *lastPtr;
    int pos, i, n,splitPos;
    int newKey, lastKey;
    enum KeyStatus value;
    if (ptr == NULL)
    {
        *newnode = NULL;
        *upKey = key;
        return InsertIt;
    }
    n = ptr->n;
    pos = searchPos(key, ptr->keys, n);
    if (pos < n && key == ptr->keys[pos])
        return Duplicate;
    value = ins(ptr->p[pos], key, &newKey, &newPtr);
    if (value != InsertIt)
        return value;
    /*If keys in node is less than M-1 where M is order of B tree*/
    if (n < M - 1)
    {
        pos = searchPos(newKey, ptr->keys, n);
        /*Shifting the key and pointer right for inserting the new key*/
        for (i=n; i>pos; i--)
        {
            ptr->keys[i] = ptr->keys[i-1];
            ptr->p[i+1] = ptr->p[i];
        }
        /*Key is inserted at exact location*/
        ptr->keys[pos] = newKey;
        ptr->p[pos+1] = newPtr;
        ++ptr->n; /*incrementing the number of keys in node*/
        return Success;
    }/*End of if */
    /*If keys in nodes are maximum and position of node to be inserted is last*/
    if (pos == M - 1)
    {
        lastKey = newKey;
        lastPtr = newPtr;
    }
    else /*If keys in node are maximum and position of node to be inserted is not last*/
    {
        lastKey = ptr->keys[M-2];
        lastPtr = ptr->p[M-1];
        for (i=M-2; i>pos; i--)
        {
            ptr->keys[i] = ptr->keys[i-1];
            ptr->p[i+1] = ptr->p[i];
        }
        ptr->keys[pos] = newKey;
        ptr->p[pos+1] = newPtr;
    }
    splitPos = (M - 1)/2;
       (*upKey) = ptr->keys[splitPos];

    (*newnode)=malloc(sizeof(struct node));/*Right node after split*/
    ptr->n = splitPos; /*No. of keys for left splitted node*/
    (*newnode)->n = M-1-splitPos;/*No. of keys for right splitted node*/
    for (i=0; i < (*newnode)->n; i++)
    {
        (*newnode)->p[i] = ptr->p[i + splitPos + 1];
        if(i < (*newnode)->n - 1)
            (*newnode)->keys[i] = ptr->keys[i + splitPos + 1];
        else
            (*newnode)->keys[i] = lastKey;
    }
    (*newnode)->p[(*newnode)->n] = lastPtr;
    return InsertIt;
}/*End of ins()*/

void display(struct node *ptr, int blanks)
{
    if (ptr)
    {
        int i;
        for(i=1;i<=blanks;i++)
            printf(" ");
        for (i=0; i < ptr->n; i++)
            printf("%d ",ptr->keys[i]);
        printf("\n");
        for (i=0; i <= ptr->n; i++)
            display(ptr->p[i], blanks+10);
    }/*End of if*/
}/*End of display()*/

void search(int key)
{
    int pos, i, n;
    struct node *ptr = root;
    printf("Search path:\n");
    while (ptr)
    {
        n = ptr->n;
        for (i=0; i < ptr->n; i++)
            printf(" %d",ptr->keys[i]);
        printf("\n");
        pos = searchPos(key, ptr->keys, n);
        if (pos < n && key == ptr->keys[pos])
        {
            printf("Key %d found in position %d of last dispalyed node\n",key,i);
            return;
        }
        ptr = ptr->p[pos];
    }
    printf("Key %d is not available\n",key);
}/*End of search()*/

int searchPos(int key, int *key_arr, int n)
{
    int pos=0;
    while (pos < n && key > key_arr[pos])
        pos++;
    return pos;
}/*End of searchPos()*/

void DelNode(int key)
{
    struct node *uproot;
    enum KeyStatus value;
    value = del(root,key);
    switch (value)
    {
    case SearchFailure:
        printf("Key %d is not available\n",key);
        break;
    case LessKeys:
        uproot = root;
        root = root->p[0];
        free(uproot);
        break;
    }/*End of switch*/
}/*End of delnode()*/

enum KeyStatus del(struct node *ptr, int key)
{
    int pos, i, pivot, n ,min;
    int *key_arr;
    enum KeyStatus value;
    struct node **p,*lptr,*rptr;

    if (ptr == NULL)
        return SearchFailure;
    /*Assigns values of node*/
    n=ptr->n;
    key_arr = ptr->keys;
    p = ptr->p;
    min = (M - 1)/2;/*Minimum number of keys*/

    pos = searchPos(key, key_arr, n);
    if (p[0] == NULL)
    {
        if (pos == n || key < key_arr[pos])
            return SearchFailure;
        /*Shift keys and pointers left*/
        for (i=pos+1; i < n; i++)
        {
            key_arr[i-1] = key_arr[i];
            p[i] = p[i+1];
        }
        return --ptr->n >= (ptr==root ? 1 : min) ? Success : LessKeys;
    }/*End of if */

    if (pos < n && key == key_arr[pos])
    {
        struct node *qp = p[pos], *qp1;
        int nkey;
        while(1)
        {
            nkey = qp->n;
            qp1 = qp->p[nkey];
            if (qp1 == NULL)
                break;
            qp = qp1;
        }/*End of while*/
        key_arr[pos] = qp->keys[nkey-1];
        qp->keys[nkey - 1] = key;
    }/*End of if */
    value = del(p[pos], key);
    if (value != LessKeys)
        return value;

    if (pos > 0 && p[pos-1]->n > min)
    {
        pivot = pos - 1; /*pivot for left and right node*/
        lptr = p[pivot];
        rptr = p[pos];
        /*Assigns values for right node*/
        rptr->p[rptr->n + 1] = rptr->p[rptr->n];
        for (i=rptr->n; i>0; i--)
        {
            rptr->keys[i] = rptr->keys[i-1];
            rptr->p[i] = rptr->p[i-1];
        }
        rptr->n++;
        rptr->keys[0] = key_arr[pivot];
        rptr->p[0] = lptr->p[lptr->n];
        key_arr[pivot] = lptr->keys[--lptr->n];
        return Success;
    }/*End of if */
    if (pos<n && p[pos+1]->n > min)
    {
        pivot = pos; /*pivot for left and right node*/
        lptr = p[pivot];
        rptr = p[pivot+1];
        /*Assigns values for left node*/
        lptr->keys[lptr->n] = key_arr[pivot];
        lptr->p[lptr->n + 1] = rptr->p[0];
        key_arr[pivot] = rptr->keys[0];
        lptr->n++;
        rptr->n--;
        for (i=0; i < rptr->n; i++)
        {
            rptr->keys[i] = rptr->keys[i+1];
            rptr->p[i] = rptr->p[i+1];
        }/*End of for*/
        rptr->p[rptr->n] = rptr->p[rptr->n + 1];
        return Success;
    }/*End of if */

    if(pos == n)
        pivot = pos-1;
    else
        pivot = pos;

    lptr = p[pivot];
    rptr = p[pivot+1];
    /*merge right node with left node*/
    lptr->keys[lptr->n] = key_arr[pivot];
    lptr->p[lptr->n + 1] = rptr->p[0];
    for (i=0; i < rptr->n; i++)
    {
        lptr->keys[lptr->n + 1 + i] = rptr->keys[i];
        lptr->p[lptr->n + 2 + i] = rptr->p[i+1];
    }
    lptr->n = lptr->n + rptr->n +1;
    free(rptr); /*Remove right node*/
    for (i=pos+1; i < n; i++)
    {
        key_arr[i-1] = key_arr[i];
        p[i] = p[i+1];
    }
    return --ptr->n >= (ptr == root ? 1 : min) ? Success : LessKeys;
}/*End of del()*/

/* Output of B Tree Program */