This document contains C code snippets demonstrating various string and file handling functions in C including: 1. Functions to get the length of a string, concatenate two strings, and search for a substring within a string. 2. Code implementing a B+ tree data structure with functions for initialization, traversal, insertion, and deletion. 3. A threaded binary tree implementation with functions for insertion, deletion, search, and printing the tree. 4. Additional examples of copying one string to another, reading from and writing to binary files, and counting the number of words in a file.

1. //String Length
#include <stdio.h>
void main()
{
char string[50];
int i, length = 0;
printf("Enter a string n");
gets(string);
for (i = 0; string[i] != '0'; i++)
{
length++;
}
printf("The length of %s = %dn", string, length);
}

2. // String Concatenation
#include<stdio.h>
void main(void)
{
char str1[25],str2[25];
int i=0, j=0;
printf("nEnter First String:");
gets(str1);
printf("nEnter Second String:");
gets(str2);
while(str1[i]!='0')
i++;
while(str2[j]!='0')
{
str1[i]=str2[j];
j++;
i++;
}
str1[i]='0';
printf("nConcatenated String is %s",str1);
}

3. //Pattern Matching
# include<stdio.h>
void main()
{
char str[80], search[10];
int count1 = 0, count2 = 0, i, j, flag;
printf("Enter a string:");
gets(str);
printf("Enter search substring:");
gets(search);
while (str[count1] != '0')
count1++;
while (search[count2] != '0')
count2++;
for (i = 0; i <= count1 - count2; i++)
{
for (j = i; j < i + count2; j++)
{
flag = 1;
if (str[j] != search[j - i])
{
flag = 0;
break;
}

4. }
if (flag == 1)
break;
}
if (flag == 1)
printf("SEARCH SUCCESSFUL!");
else
printf("SEARCH UNSUCCESSFUL!");
}

5. // Program to Implement B+ Tree
#include<stdio.h>
#include<conio.h>
#include<iostream>
using namespace std;
struct BTreeNode
{
int *data;
BTreeNode **child_ptr;
bool leaf;
int n;
}*root = NULL, *np = NULL, *x = NULL;
BTreeNode * init()
{
int i;
np = new BTreeNode;
np->data = new int[5];
np->child_ptr = new BTreeNode *[6];
np->leaf = true;
np->n = 0;
for (i = 0; i < 6; i++)
{
np->child_ptr[i] = NULL;
}
return np;

6. }
void traverse(BTreeNode *p)
{
cout<<endl;
int i;
for (i = 0; i < p->n; i++)
{
if (p->leaf == false)
{
traverse(p->child_ptr[i]);
}
cout << " " << p->data[i];
}
if (p->leaf == false)
{
traverse(p->child_ptr[i]);
}
cout<<endl;
}
void sort(int *p, int n)
{
int i, j, temp;
for (i = 0; i < n; i++)
{
for (j = i; j <= n; j++)
{

7. if (p[i] > p[j])
{
temp = p[i];
p[i] = p[j];
p[j] = temp;
}
}
}
}
int split_child(BTreeNode *x, int i)
{
int j, mid;
BTreeNode *np1, *np3, *y;
np3 = init();
np3->leaf = true;
if (i == -1)
{
mid = x->data[2];
x->data[2] = 0;
x->n--;
np1 = init();
np1->leaf = false;
x->leaf = true;
for (j = 3; j < 5; j++)
{
np3->data[j - 3] = x->data[j];

8. np3->child_ptr[j - 3] = x->child_ptr[j];
np3->n++;
x->data[j] = 0;
x->n--;
}
for(j = 0; j < 6; j++)
{
x->child_ptr[j] = NULL;
}
np1->data[0] = mid;
np1->child_ptr[np1->n] = x;
np1->child_ptr[np1->n + 1] = np3;
np1->n++;
root = np1;
}
else
{
y = x->child_ptr[i];
mid = y->data[2];
y->data[2] = 0;
y->n--;
for (j = 3; j < 5; j++)
{
np3->data[j - 3] = y->data[j];
np3->n++;
y->data[j] = 0;

9. y->n--;
}
x->child_ptr[i + 1] = y;
x->child_ptr[i + 1] = np3;
}
return mid;
}
void insert(int a)
{
int i, temp;
x = root;
if (x == NULL)
{
root = init();
x = root;
}
else
{
if (x->leaf == true && x->n == 5)
{
temp = split_child(x, -1);
x = root;
for (i = 0; i < (x->n); i++)
{
if ((a > x->data[i]) && (a < x->data[i + 1]))
{

10. i++;
break;
}
else if (a < x->data[0])
{
break;
}
else
{
continue;
}
}
x = x->child_ptr[i];
}
else
{
while (x->leaf == false)
{
for (i = 0; i < (x->n); i++)
{
if ((a > x->data[i]) && (a < x->data[i + 1]))
{
i++;
break;
}
else if (a < x->data[0])

11. {
break;
}
else
{
continue;
}
}
if ((x->child_ptr[i])->n == 5)
{
temp = split_child(x, i);
x->data[x->n] = temp;
x->n++;
continue;
}
else
{
x = x->child_ptr[i];
}
}
}
}
x->data[x->n] = a;
sort(x->data, x->n);
x->n++;
}

12. int main()
{
int i, n, t;
cout<<"enter the no of elements to be insertedn";
cin>>n;
for(i = 0; i < n; i++)
{
cout<<"enter the elementn";
cin>>t;
insert(t);
}
cout<<"traversal of constructed treen";
traverse(root);
getch();
}

13. //Threaded Binary Tree
#include <iostream>
#include <cstdlib>
#define MAX_VALUE 65536
using namespace std;
/* Class Node */
class Node
{
public:
int key;
Node *left, *right;
bool leftThread, rightThread;
};
/* Class ThreadedBinarySearchTree */
class ThreadedBinarySearchTree
{
private:
Node *root;
public:
/* Constructor */
ThreadedBinarySearchTree()
{

14. root = new Node();
root->right = root->left = root;
root->leftThread = true;
root->key = MAX_VALUE;
}
/* Function to clear tree */
void makeEmpty()
{
root = new Node();
root->right = root->left = root;
root->leftThread = true;
root->key = MAX_VALUE;
}
/* Function to insert a key */
void insert(int key)
{
Node *p = root;
for (;;)
{
if (p->key < key)
{
if (p->rightThread)
break;
p = p->right;
}

15. else if (p->key > key)
{
if (p->leftThread)
break;
p = p->left;
}
else
{
/* redundant key */
return;
}
}
Node *tmp = new Node();
tmp->key = key;
tmp->rightThread = tmp->leftThread = true;
if (p->key < key)
{
/* insert to right side */
tmp->right = p->right;
tmp->left = p;
p->right = tmp;
p->rightThread = false;
}
else
{

16. tmp->right = p;
tmp->left = p->left;
p->left = tmp;
p->leftThread = false;
}
}
/* Function to search for an element */
bool search(int key)
{
Node *tmp = root->left;
for (;;)
{
if (tmp->key < key)
{
if (tmp->rightThread)
return false;
tmp = tmp->right;
}
else if (tmp->key > key)
{
if (tmp->leftThread)
return false;
tmp = tmp->left;
}
else

17. {
return true;
}
}
}
/* Fuction to delete an element */
void Delete(int key)
{
Node *dest = root->left, *p = root;
for (;;)
{
if (dest->key < key)
{
/* not found */
if (dest->rightThread)
return;
p = dest;
dest = dest->right;
}
else if (dest->key > key)
{
/* not found */
if (dest->leftThread)
return;
p = dest;

18. dest = dest->left;
}
else
{
/* found */
break;
}
}
Node *target = dest;
if (!dest->rightThread && !dest->leftThread)
{
/* dest has two children*/
p = dest;
/* find largest node at left child */
target = dest->left;
while (!target->rightThread)
{
p = target;
target = target->right;
}
/* using replace mode*/
dest->key = target->key;
}
if (p->key >= target->key)
{

19. if (target->rightThread && target->leftThread)
{
p->left = target->left;
p->leftThread = true;
}
else if (target->rightThread)
{
Node *largest = target->left;
while (!largest->rightThread)
{
largest = largest->right;
}
largest->right = p;
p->left = target->left;
}
else
{
Node *smallest = target->right;
while (!smallest->leftThread)
{
smallest = smallest->left;
}
smallest->left = target->left;
p->left = target->right;
}

20. }
else
{
if (target->rightThread && target->leftThread)
{
p->right = target->right;
p->rightThread = true;
}
else if (target->rightThread)
{
Node *largest = target->left;
while (!largest->rightThread)
{
largest = largest->right;
}
largest->right = target->right;
p->right = target->left;
}
else
{
Node *smallest = target->right;
while (!smallest->leftThread)
{
smallest = smallest->left;
}

21. smallest->left = p;
p->right = target->right;
}
}
}
/* Function to print tree */
void printTree()
{
Node *tmp = root, *p;
for (;;)
{
p = tmp;
tmp = tmp->right;
if (!p->rightThread)
{
while (!tmp->leftThread)
{
tmp = tmp->left;
}
}
if (tmp == root)
break;
cout<<tmp->key<<" ";
}
cout<<endl;

22. }
};
int main()
{
ThreadedBinarySearchTree tbst;
cout<<"ThreadedBinarySearchTree Testn";
char ch;
int choice, val;
/* Perform tree operations */
do
{
cout<<"nThreadedBinarySearchTree Operationsn";
cout<<"1. Insert "<<endl;
cout<<"2. Delete"<<endl;
cout<<"3. Search"<<endl;
cout<<"4. Clear"<<endl;
cout<<"Enter Your Choice: ";
cin>>choice;
switch (choice)
{
case 1 :
cout<<"Enter integer element to insert: ";
cin>>val;
tbst.insert(val);

23. break;
case 2 :
cout<<"Enter integer element to delete: ";
cin>>val;
tbst.Delete(val);
break;
case 3 :
cout<<"Enter integer element to search: ";
cin>>val;
if (tbst.search(val) == true)
cout<<"Element "<<val<<" found in the tree"<<endl;
else
cout<<"Element "<<val<<" not found in the tree"<<endl;
break;
case 4 :
cout<<"nTree Clearedn";
tbst.makeEmpty();
break;
default :
cout<<"Wrong Entry n ";
break;
}
/* Display tree */
cout<<"nTree = ";
tbst.printTree();

24. cout<<"nDo you want to continue (Type y or n): ";
cin>>ch;
}
while (ch == 'Y'|| ch == 'y');
return 0;
}

25. //To Copy one string into other
#include <stdio.h>
int main()
{
char s1[100], s2[100], i;
printf("Enter string s1: ");
gets(s1);
printf("Enter string s2: ");
gets(s2);
for(i = 0; s1[i] != '0'; ++i)
{
s2[i] = s1[i];
}
s2[i] = '0';
printf("String s1: %s", s1);
printf("nString s2: %s", s2);
return 0;
}

26. // Read from binary file
#include <stdio.h>
struct threeNum
{
int n1, n2, n3;
};
int main()
{
int n;
struct threeNum num;
FILE *fptr;
if ((fptr = fopen("C:program.bin","rb")) == NULL){
printf("Error! opening file");
// Program exits if the file pointer returns NULL.
exit(1);
}
for(n = 1; n < 5; ++n)
{

27. fread(&num, sizeof(struct threeNum), 1, fptr);
printf("n1: %dtn2: %dtn3: %d", num.n1, num.n2, num.n3);
}
fclose(fptr);
return 0;
}

28. //To count number of words
#include<stdio.h>
void main()
{
FILE *p;
char ch;
int w=1;
clrscr();
p=fopen("source","r");
if(p==NULL)
{
printf("file not found");
}
else
{
ch=fgetc(p);
while(ch!=EOF)
{
printf("%c",ch);
if(ch==' '||ch=='n')
{
w++;
}
ch=fgetc(p);
}
printf("nWords in a file are=%d",w);
}
fclose(p);
getch();
}

29. //writing into a binary file
#include <stdio.h>
struct threeNum
{
int n1, n2, n3;
};
int main()
{
int n;
struct threeNum num;
FILE *fptr;
if ((fptr = fopen("C:program.bin","wb")) == NULL){
printf("Error! opening file");
// Program exits if the file pointer returns NULL.
exit(1);
}
for(n = 1; n < 5; ++n)
{
num.n1 = n;
num.n2 = 5n;
num.n3 = 5n + 1;
fwrite(&num, sizeof(struct threeNum), 1, fptr);
}
fclose(fptr);
return 0;