Strings

Module  1: Strings

• Formatted input and output: character

• Formatted input and output: string

• Unformatted input and output: character

• Unformatted input and output: string

• Printing individual characters of strings

• Convert from lowercase to uppercase using library function

• Convert from uppercase to lowercase using library function

• Length of the string using library function

• Length of the string without using library function

• Reversing a String using library function

• Reversing a String without using library function  

• String copy using library function

• String copy without using library function

• String concatenation using library function

• String concatenation without using library function  

• String comparison using library function

• String comparison without using library function

• Array of strings

• Insert a substring to string at a valid position

• Extract a substring from string 

• Find all occurrences of substring  in a string

• Delete all occurrences of substring from a string

• Delete the substring of length n from the string at specified position (pos)

Delete all occurrences of pattern from a string

Delete all occurrences of pattern (pat) from a string (txt)

#include<stdio.h>

#include<string.h>

void main()

{

                char txt[30],  pat[30];

                int m, n;

                int i, j, found = 0;

                printf("\nEnter the main string:");

                gets(txt);

                printf("\nEnter the pattern to be searched: ");

                gets(pat);

                m = strlen(txt);

                n = strlen(pat);

                for(i=0;  i<=m-n;  i++)

                {

                                found  = 1;

                                for(j=0; j<n; j++)

                                {

                                                if(txt[i+j] != pat[j])

                                                {

                                                                found = 0;

                                                                break;

                                                }

                                }

                                if(found == 1)

                                {

                    /* If pattern is found then shift all characters to left and decrement the string length */

                                                for(j=i;  j<m -n; j++)

                                                {

                                                                txt[j] = txt[j+n];

                                                }

                                                txt[j] = '\0';

                                                m = m - n;

                                 }

                }

                if(found == 0)

                                printf("\nPattern not found");

                else

                {

                                printf("\nAfter deleting pattern the string is: ");

                                puts(txt);

                }

}

Output:

Enter the main string:    hello hii how hii

Enter the pattern to be searched:   hii

After deleting pattern the string is: hello    how

Enter the main string:    hello hii how hii

Enter the pattern to be searched: abc

Pattern not found

Sparse Matrix: Fast Transpose

Sparse Matrix: Fast Transpose

#include<stdio.h>

#include<stdlib.h>

#define MAX 100

typedef struct

{

            int row;

            int col;

            int val;

}sparse;

void readsparse(sparse a[], int m, int n)

{

            int i, j, k, item, p;

            a[0].row = m;

            a[0].col = n;

            k = 1;

            printf("\nEnter the elements:\n");

            for(i=0; i<m; i++)

            {

                        for(j=0; j<n; j++)

                        {

                                    scanf("%d",&item);

                                    if(item == 0)

                                                continue;

                                    a[k].row = i;

                                    a[k].col = j;

                                    a[k].val = item;

                                    k++;

                        }

            }

            a[0].val = k-1;

            printf("\nThe entered sparse matrix is:\n");

            printf("\nRow\tColumn\tValue\n");

            for(p=0;  p<=a[0].val;  p++)

            {

                        printf("%d\t", a[p].row);

                        printf("%d\t", a[p].col);

                        printf("%d\n", a[p].val);

            }

}

void fast_transpose(sparse a[],  sparse b[])

{

            int row_terms[100],  start_pos[100];

            int i,  j,  p;       

            int numTerms = a[0].val;

            int numCols = a[0].col;

             

            b[0].row = numCols;

            b[0].col = a[0].row;

            b[0].val = numTerms;

            if(numTerms>0)

            {

                        for(i =0; i<numCols;  i++)

                                                row_terms[i] = 0;

                        for(i=1; i<=numTerms; i++)

                                                row_terms[a[i].col]++;

                        start_pos[0]=1;

                        for(i=1; i<numCols; i++)

                                                start_pos[i] = start_pos[i-1] + row_terms[i-1];

                        for(i=1; i<=numTerms; i++)

                        {

                                                j = start_pos[a[i].col]++;

                                    b[j].row = a[i].col;

                                                b[j].col = a[i].row;

                                                b[j].val = a[i].val;

                        }

             }

            printf("\nThe Fast Transpose sparse matrix is:\n");

            printf("\nRow\tColumn\tValue\n");

            for(p=0; p<=a[0].val; p++)

            {

                        printf("%d\t", b[p].row);

                        printf("%d\t", b[p].col);

                        printf("%d\n", b[p].val);

            }

}

void main()

{

            int m, n, key;

            sparse a[MAX], b[MAX];

            printf("\nEnter  the no of rows and columns:\t");

            scanf("%d%d",&m, &n);

            readsparse(a, m, n);

             fast_transpose(a, b);

}

Output:

Enter  the no of rows and columns:      6 6

Enter the elements:

15   0   0   22   0   -15

0   11   3   0    0   0

0   0   0   -6   0   0

0   0    0    0   0   0

91  0   0   0   0   0

0   0   28  0   0   0

The entered sparse matrix is:

Row     Column  Value

6       6       8

0       0       15

0       3       22

0       5       -15

1       1       11

1       2       3

2       4       -6

4       1       91

5       3       28

The Fast Transpose sparse matrix is:

Row    Column           Value

6          6                      8

0          0                      15

1          1                      11

1          4                      91

2          1                      3

3          0                      22

3          5                      28

4          2                      -6

5          0                      -15

Find all occurrences of pattern in a string

Find all occurrences of pattern(pat) in a a string(txt)

#include<stdio.h>

#include<string.h>

void main()

{

                char txt[30],  pat[30];

                int m, n;

                int i, j, found = 0;

                printf("\nEnter the main string:");

                gets(txt);

                printf("\nEnter the pattern to be searched: ");

                gets(pat);

                m = strlen(txt);

                n = strlen(pat);

                for(i=0;  i<=m-n;  i++)

                {

                                found  = 1;

                                for(j=0; j<n; j++)

                                {

                                                if(txt[i+j] != pat[j])

                                                {

                                                                found = 0;

                                                                break;

                                                }

                                }

                                if(found == 1)

                                                printf("\n The pattern found at index:%d",  i);

                }

                if(found  ==  0)

                                printf("\n   Pattern not found");

}

Output:

Enter the main string:    hello hii how hii

Enter the pattern to be searched:    hii

The pattern found at index:  6

The pattern found at index:   14

Extract a substring from a string from specified position

Extract a substring (substr) of length n from a string (str) from specified position (pos)

#include<stdio.h>

void main()

{

                char str[20], substr[20];

                int n, pos, i, j=0;

                printf("\nEnter the string:");

                gets(str);

                printf("\nEnter the position:");

                scanf("%d", &pos);

                printf("\nEnter the length of substring:");

                scanf("%d", &n);

                i = pos;

                while(str[i] != '\0'  &&  n>0)

                {

                                substr[j] = str[i];

                                i++;

                                j++;

                                n--;

                }

                substr[j] = '\0';

                printf("\nThe substring is:");

                puts(substr);

}

Output:

Enter the string:               hello hii abc

Enter the position:          2

Enter the length of substring:     5

The substring is:               llo h

Insert a substring to a string at specified position

Insert a substring (str) to a string (txt) at specified position (pos)

#include<stdio.h>
#include<string.h>

void main()
{
          char txt[30], str[30];
          int pos, i, k=0,m,n;
          printf("\nEnter the text: ");
          gets(txt);
          printf("\nEnter the string to be inserted: ");
          gets(str);
          printf("\nEnter the position where to be inserted: ");
          scanf("%d", &pos);
          m = strlen(txt);
          n = strlen(str);

          for(i=m-1; i>=pos; i--)
          {
                    txt[i+n] = txt[i];
          }
           i = pos;
           while(str[k] != '\0')
          {
                  txt[i] = str[k];
                   i++;
                   k++;
           }
           m = m+n;
           txt[m] = '\0';

           printf("\nThe new string is: ");
           puts(txt);
}

Output:
Enter the text: abcdefghij
Enter the string to be inserted: yyyy
Enter the position where to be inserted: 2
The new string is:  abyyyycdefghij

---------------------------------------------------------------------------------------------------

/*Method 2*/

#include<stdio.h>

void main()

{

                char txt[30],  str[30], new[40];

                int pos,  j=0, i=0, k=0;

                printf("\nEnter the text: ");

                gets(txt);

                printf("\nEnter the string to be inserted: ");

                gets(str);

                printf("\nEnter the position where to be inserted: ");

                scanf("%d", &pos);

                while(txt[i] != '\0' )

                {

                                if(i == pos)

                                {

                                                while(str[k] != '\0')

                                                {

                                                                new[j] = str[k];

                                                                j++;

                                                                k++;

                                                }

                                }

                                new[j] = txt[i];

                                j++;

                                i++;

                }

                new[j] = '\0';

                printf("\nThe new string is: ");

                puts(new);

}

Output:

Enter the text:                                            how are you

Enter the string to be inserted:                  abcde

Enter the position where to be inserted:    1

The new string is:                                      habcdeow are you

Copy one string to another without using library function strcpy

Copy one string to another without using library function strcpy

#include<stdio.h>

main()

{

                char s1[10], s2[10];

                int n, i = 0;

                printf("\nEnter string 2: ");

                gets(s2);

                while(s2[i] != 0)

                {

                                s1[i] = s2[i];

                                i++;

                }

                s1[i] = '\0';

                printf("\n String 1 after copying: ");

                puts(s1);

}

Output:

Enter string 2: Hello Hii

String 1 after copying: Hello Hii

Reversing the string without using Library function

Reversing the string without using Library function

#include<stdio.h>

#include<string.h>

void main()

{

                char str[20], rev[20], temp;

                int i=0, j;

                printf("\nEnter the string: ");

                gets(str);

                j = strlen(str) - 1;

                while(i<j)

                {

                                temp = str[j];

                                str[j] = str[i];

                                str[i] = temp;

                                i++;

                                j--;

                }

                printf("\nReversed string: ");

                puts(str);

}

Output:

Enter the string:   newspaper

Reversed string:   repapswen

Also check,
https://tejaswinihbhat.blogspot.in/2016/08/strrev-reversing-string-using-library.html

strrev: Reversing the string using library function

String: strrev(string)

Reversing the string using library function

#include<stdio.h>          

#include<string.h>

main()

{

                char s[60];

                printf("\nEnter string:\t");

                gets(s);

                printf("\nReversed string is:  %s", strrev(s));

}

Output:

Enter string:   Hello How Are You

Reversed string is:  uoY erA woH olleH

strncpy: Copy specified number of characters from one string to another string using library function

String: strncpy(dest, source, n)

Copy specified number of characters from one string to another string using library function

#include<string.h>

main()

{

                char s[60], d[60]="\0";

                printf("\nSource string:\t");

                gets(s);

                strncpy(d, s, 5);

                printf("\nDestination string: %s", d);

}

Output:

Source string:  Hii How Are you

Destination string: Hii H

strcpy: Copy one string to another string using library function

String: strcpy(dest, source)

Copy one string to another string using library function

#include<stdio.h>

#include<string.h>

main()

{

                char s[60], d[60]="\0";

                printf("\nSource string:\t");

                gets(s);

                strcpy(d, s);

                printf("\nDestination string: %s", d);

}

Output:

Source string:  Hii How Are you

Destination string: Hii How Are you

strupr: Convert from Lower case to Upper case using Library function

String: strupr(string)

Convert from Lower case to Upper case using Library function

#include<stdio.h>

#include<string.h>

main()

{

                char s[60];

                printf("\nEnter string:\t");

                gets(s);

                printf("\nString in uppercase: %s", strupr(s));

}

Output:

Enter string:   Hello How Are You

String in uppercase: HELLO HOW ARE YOU