The Complete Codes

Mono Alphabetic Cipher Encryption-Decryption Introduction It is Better than Caesar Cipher. If, instead the “cipher” line can be any permutation of the key 26 alphabetic characters, then there are 26! Or greater than 4 * 10 26  possible keys. This is 10 orders of magnitude greater than the key space for DES and would seem to as a Mono-alphabetic substitution cipher, because a single cipher alphabet is used per message. There is however, another line of attack. If one analytically knows the nature of the plain text, then the analyst can exploit the regularities of the language. Limitations Monoalphabetic ciphers are easy to break because they reflect the frequency data of the original alphabet. A countermeasure is to provide multiple substitutes, known as homophones, for a single letter C Progrm to Encryp the imputed text using Mono Alphabetic Cipher. #include <stdio.h> #include <string.h> int main () {     char pt [ 52 ] = { 'A' , 'B' , 'C' ,

Recurrences And Their Solution Methods Recursion Tree Just Simplification of Iteration method: Consider The Recurrences Second Example Example Three Master Method Cookbook solution for some recurrences of the form T(n) = a . T(n/b) + f(n) where a>=1, b>1, f(n) asymptotically positive Describe its cases 

Recurrences Recursive algorithms are described by using recurrence relations. A recurrence is an inequality that describes a problem in terms of itself. For Example: Recursive algorithm for finding factorial   T(n)=1     when n =1 T(n)=T(n-1) + O(1)    when  n>1 Recursive algorithm for finding Nth Fibonacci number T(1)=1     when n=1 T(2)=1     when n=2 T(n)=T(n-1) + T(n-2) +O(1)     when n>2 Recursive algorithm for binary search T(1)=1     when n=1 T(n)=T(n/2) + O(1)    when n>1 Techniques for Solving Recurrences We’ll use four techniques: Iteration method Recursion Tree Substitution Master Method   – for divide & conquer Characteristic Equation   – for linear Iteration method Expand the relation so that summation independent on n is obtained. Bound the summation e.g.    T(n)= 2T(n/2) +1  when n>1 T(n)= 1    when n=1 T(n) = 2T(n/2) +1           = 2 { 2T(n/4) + 1} +1           = 4T(n/4) + 2 + 1           =

C Program To Check The String Is Valid Identifier Or Not #include <stdio.h> #include <conio.h> #include <string.h> int main () { char string [ 25 ]; int count= 0 ,flag; printf ( "Enter any string: " ); gets (string); if ( ( string [ 0 ]>= 'a' && string [ 0 ]<= 'z' )||( string [ 0 ]>= 'A' && string [ 0 ]<= 'Z' )||( string [ 0 ]== '_' )) {     for ( int i= 1 ;i<= strlen (string);i++)     {         if (( string [i]>= 'a' && string [i]<= 'z' )||( string [i]>= 'A' && string [i]<= 'Z' )||( string [i]>= '0' && string [i]<= '9' )||( string [i]== '-' ))     {     count++;     }        }     if (count== strlen (string))     {       flag= 0 ;     } } else {     flag= 1 ; } if (flag== 1 )     printf ( " %s is not valid identifier" ,string); else     printf ( " %s is valid ident

C Program To Accept The String Starting With 01 And Ending With 011 #include <stdio.h> #include <string.h> int main () {     char str [ 10 ];     int len, i, q = 0 ;     printf ( "enter the string which only contain 0 and 1 \n " );     scanf ( " %s " , str);     len = strlen (str);     for (i = 0 ; i <= len; i++)     {         if ( str [i] == '0' && q == 0 )             q = 1 ;         else if ( str [i] == '1' && q == 0 )             q = 6 ;         else if ( str [i] == '0' && q == 1 )             q = 6 ;         else if ( str [i] == '1' && q == 1 )             q = 2 ;         else if ( str [i] == '0' && q == 2 )             q = 3 ;         else if ( str [i] == '1' && q == 2 )             q = 2 ;         else if ( str [i] == '0' && q == 3 )             q = 3 ;         else if ( str [i] == '1' &&a

C Program To Accept The String Starting With ab And Ending With abb  #include <stdio.h> #include <string.h> int main ( int argc , char const * argv []) {     char str [ 10 ];     int len, i, q = 0 ;     printf ( "enter the string which only contain a and b \n " );     scanf ( " %s " , str);     len = strlen (str);     for (i = 0 ; i <= len; i++)     {         if ( str [i] == 'a' && q == 0 )             q = 1 ;         else if ( str [i] == 'b' && q == 0 )             q = 6 ;         else if ( str [i] == 'a' && q == 1 )             q = 6 ;         else if ( str [i] == 'b' && q == 1 )             q = 2 ;         else if ( str [i] == 'a' && q == 2 )             q = 3 ;         else if ( str [i] == 'b' && q == 2 )             q = 2 ;         else if ( str [i] == 'a' && q == 3 )             q = 3 ;         else i

Variables in C Programmings:- "Variable in C" variables names are case sensitive whose value can change any time. It is a memory location used to store data value. A variable name in C variables should be carefully chosen so that its use is reflected in a useful way in the entire program.  Rules for declaring variables in C Programming:- They must always begin with a letter, although some systems permit underscore as the first character. The length of a variable must not be more than 8 characters. White space is not allowed and A variable should not be a Keyword It should not contain any special characters.  In C variables A variable declaration provides assurance to the compiler that there exists a variable with the given type and name so that the compiler can proceed for further compilation without requiring the complete detail about the variable. A variable definition has its meaning at the time of compilation only, the compiler needs actual variable