Art of Understanding an Algorithm

For Understanding the Algorithm. You first need to fascinate by its practical working.

After that Break that whole practical action into smallest step possible and Analyse each step that cause that whole magic

Try to come out from comfort zone and try till you not reach for success

Some Basic Algorithms from which you can start brushing up you skills

1) Bubble Sort

......other sorting techniques

stack

queue

circular queue

Make practical programs for all

Watch the Below Video in Silent Mode.It will give you the guidance How practically you should understand the algorithum

Inheritance

Pointer :C/C++ brush up

int a;
&a                                  address of a
int *p                              capable of storing address of a non pointer
int **p                            capable of storing address of a pointer .this is also known as double pointer

Let us consider and code to understand above concept better

1. int *p;
2. int **c;
3. int a[ ]={1,2,3,4};
4. *p=a;                      //*p gives value of a[0] i.e 1                                  
5. **c=&p;                 //c gives value(pointer stores address in its value) of p pointer 2293552
6.                                //**c gives address of p pointer
7.                                //*c --check yourself ! I don't Know
8. printf("%u",p);       //p gives address of a[0] 2293548  
9. *(a+i) is same as a[i]              
10. (a+i) is same as a or &a

Notations for 2-D array

1. //  in 1-d array you write int*p=a; but if a is 2-d array then this statement will give error
2. int b[2][3]={ {1,2,3} , {3,4,2} };  //here b[0] occupy 8 bytes as 2 x {[0],[1],[2],[4]}=2 x 4=8 
3. 
   
4. int(*p)[3]=b;       <--correct statement
5. printf("%d",*b); / printf("%d",b[0]); / printf("%d",&b[0][0]); / printf("%d",b);printf("%d",&b[0]); <--means an address of first element.first row b[0][0]
6. .
7. printf("%d",*(*b+1)); <--means value at b[0][1] which is 2
8. .
9. Concluded: b[i][j]=*(b[i]+j) / *(*(b+i)+j) 
10. .
11. .
12. 
    
13. printf("%d",b+1);/printf("%d",*(b+1));/printf("%d",b[1]);/printf("%d",&b[1][0]);<--means 
14.                                                 //address of first element second row b[1][0]
15. 
    
16. printf("%d",*(b+1)+2);.  //means address of b[1][2]
17. 
    

Notations for 3-D array

1. int c[3][2][2]={     {{2,5},{7,9}}  , {{3,4},{6,1}} , {{0,8},{11,13}}  };
2.  c[i][j][k]
3. printf("%d",*c)  / printf("%d",c[0])  / printf("%d",c[0][0]) <--addr of c[0][0][0]
4. 
   
5.  printf("%d",*(c[1]+1))/ / printf("%d",c[1][1])/ / printf("%d",&c[1][1][0])<--addr of c[1][1][0]
6.                                        printf("%d",*(c[0][1]+1)) <--value of c[0][1][1];
7. i.e c[i][j][k]= / printf("%d",*(c[i][j]+k));/printf("%d",*(*(c[i]+j)+k));/printf("%d",*(*(*(c+i)+j)+k));

Do you Know ?

• loop pointer move by size of data type
• scanf has &a to take value
• printf has just a to print value
• in array no need to write & while passing address

type specifier for printing a address--%u

Ways of Passing Array from Function: C/C++ Brush up

In programming we make a call by two methods
1)call by value- Pass a value
2)call by reference - Pass a address and fun taking this address should have pointer.And also to                                            display result again pointer.

Array is passed to a function using Call be reference.

There is Two ways

1) Using &

1. void main( )
2. {
3. int a[5]={1,2,3,4,5}
4. for(int i=0 ; i<=4 ;i++)
5.   {
6. printarray(&a[0]);    //or printarray(&a);[NOT SURE]
7.    }
8. }
9. .
10. .
11. .
12. .
13. void printarray(int *p)
14. {
15. printf("%d",*p);
16. }

2) Without Using &

1. void main( )
2. {
3. int a[5]={1,2,3,4,5}
4. 
   
5. printarray(a);  
6.    
7. }
8. .
9. .
10. .
11. .
12. void printarray(int *p)
13. {
14. for(int i=0 ; i<=4 ;i++)
15.   {
16. printf("%d",*p);
17.    }
18. }
19. }

Passing Character Array through a Function

STRING IS THE ARRAY OF CHARACTER WITH ONE NULL '\O' CHARACTER IN THE END

There is 4 ways of initilizing a character

1) 

1. char c[4];
2. c[0]='j'; c[1]='o'; c[2]='h'; c[3]='n'; c[4]='\0';

2)

1. c[ ]={'j','o','h','n','\0'}

3)Using String Literal

1. c[ ]="john";

4) Using Pointer

1. char*c="Hellow";

1. int main( )
2. {
3. char *c="Hellow";
4. print( c)
5. .
6. return(0);
7. .
8. }
9. .
10. .
11. .
12. .
13. ..
14. .
15. void print(char *c)
16. {
17. int i=0;
18. while( *(c+i)!= '\0') )
19. {
20. printf("%c",c[i]);
21. i++;
22. }
23. printf("\n");
24. }
25. .
26. .//or
27. .
28. .
29. .
30. .
31. .
32. void print(char *c)
33. {
34. while( *(c)!= '\0') )
35. {
36. printf("%c",c[i]);
37. c++;
38. }
39. printf("\n");

Passing a 2-Dimentional Array through a Function

while passing two dimensional array to function last dimension is compulsory

1. int func (int a[ ][3])
2. {
3. .
4. .
5. .
6. .
7. .}

Passing a 3-Dimentional Array

1. int func (int a[ ][2][2])  / (int (*a)[2][2])
2. {
3. .
4. .
5. .
6. .
7. .}

STL:Stack and queue C/C++ brush up

STL:Standard Temparary Library

In RAM and we have a stack memory !

Now in Programming we store our data in stack or queue . and we implements these
using data structure
1)Array
or
2)Link List
or
3)Trees.

all these data structures are interconnected .you can create array to queue ,queue to array

Stack

Operations on stack

1. Push
2. Pop
3. Is Full
4. Is Empty

--Exbhibit LIFO (Last in first out)
--Here in stack we have have one pointer only

1. Top 

Push

S-our stack array
N-size of our stack array
Top-stack pointer
x-element to be pushed

1. push(S,N,Top,x)
2. {
3.    if(Top+1==N)
4.       {
5.      printf("Stack Overflow");
6.      exit;
7.       }
8. else
9.     {
10.       Top++;
11.        S[Top]=x;
12. }

Pop

--here we are only delecting the top most element of stack array S. as here we what to return the elemet which would be de;leted so for that we will use int return type of following function

1. int pop(S,N,Top)
2. {
3.       int y;
4.       if (Top==-1)
5.         {
6.        printf("Stack Underflow");
7.        exit;
8.         }
9. else
10.         {
11.        y=S[Top];
12.        Top--;
13.        return y;
14. }

Queue

Operations on queue

1. Enqueue-Data Insert  <--->Push in stack
2. Dequeue- Data Delete
3. Is Full
4. Is Empty

--Here in an array of queue we have two pointer

1. front--Tells deletion
2.  rear--Tells insertion

Enqueue

in below code

Q-Our Array

N-Size of our array

F-Front pointer of our queue

R-Rear pointer of our queue

x-element we want to put

1. void enqueue(Q,N,F,R,x)
2. {
3.      if(R+1==N)  //means if R+1 ==size of an array
4.        {
5.         printf("Queue is overflow");
6.         exit;
7.         }
8.    else if
9.        {
10.        if(F==R==-1)
11.          {
12.            F=R=0;
13.           }
14.         else
15.            {
16.             R=R+1;
17.            }
18. Q[R]=x;
19. }

Dequeue

Here no x .because our aim is to just delete one element which is always from front and we also want what is the value of deleted array that's why we are returning from our function.

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

^                             ^

Front                    Rear(insertion)

(Deletion)

1. int dequeue(Q,N,F,R)
2. {
3.    int y;
4.    if(F==R==-1)
5.       {
6.      prinf("underflow");
7.      exit;
8.      }
9.    else
10.      {
11.        y=Q[F]; //delete
12.         if (F==R)  //means in case if all element is before F is already deleted i.e null and we 
13.                          //know after R there is nothing So , Both R & F vacant in makes no sense so
14.                          //to get rid of that Awkward situation we are placing both in front.And
15.                        
16.            {
17.               F=R=-1;
18.             }
19.         else
20.           F=F+1;
21.        return y;
22.         }
23. }

Typecasting C/C++ Brush up

WHEN SOME BIG SPACE DATA TRY TO INSERT IN SMALL SPACE DATATYPE THERE OCCUR'S AN ERROR SO TO REMOVE THAT ERROR WE DO TYPE CASTING.

suppose you have two datatypes let say
int a=2;                      [2 byte]  (int a=300 will be stored in meom as 00101100 00000001
float b=3.2;                [4 byte]

Now in case you write an instruction

a=b;          i.e [2 byte]<--[4 byte] then it will give error

so, for that you need to type cast above 4 byte float data type into int

i.e a=(int)b;    Now it will not give any error

Let's Here only discus the Meomory allocation in array How data will store in
int a[5]={300,301,302,20,40}

300=00000001  00101100 but in meomory  first LSB is stored then MSB
similarly 301= 00000001 00101101
i.e as 00101100 00000001  and then for 301..302..20..40


further

let i have
int a[5]={300,301,302,20,40};
int *b;
int *b=a ; /  int *b=&a;   ----OK NO ERROR
char*c;
(char*)c=a; <--NO ERROR IT WILL GIVE U ONLY 1 BYTE FROM INT.
*c=a;  ---ERROR   [1byte]<--[2byte]
*c=(char*)a;---OK,NO ERROR

float *d;
*d=a; [4 byte]<--[2byte] Ok, NO ERROR.

in arithmatic typecasting is done automatically

1. #incude <stdio.h>
2. #include <conio.h>
3. 
   
4. int main()
5. {
6.     int a=20;
7.     char k;
8.     printf("type casted k=(char)a ");
9.     k=(char)a;
10.     printf("the value of k=%c\n",k);
11.     printf("type casted a=k ");
12.     k='a';
13.     a=k;
14.     printf("the value of a=%c\n",(char)a);
15. 
    
16. getch();
17. return 0;
18. }

Storage Class C / C++ Brush up

C language

Storage Class
storage classes tell you about for things

1. initial value
2. meomory location
3. scope of variable
4. lifetime of variable

1)auto -meomory create at run time

-declare inside main( )

-in variable default is auto 

1. //even if u don't write auto then also program works same
2. #include<stdio.h>
3. #include<conio.h>
4.  
5. int main()
6. {
7.     double goa;
8.     auto int i;          //here i don't have any value therefore it will print some garbage value 
9.     printf("i=%d",i);
10. goa=addi();
11.  printf("goa i=%d",goa);
12. getch();
13. return 0;
14. }
15. 
    
16. 
    
17. int addi()     /
18. {
19.     auto int i ;   
20.     printf("add i=%d",i);  //now here i value will change as this is auto and scope of that i ended
21.     return i;
22. }
23. /*u know how scope overs ? i tell u this code works in stack area of ram and when scope overs
24. then in stack meomory previous i value get poped i.e it get deleted.
25. and Now as soon as i get initialised in addi() at that time lifetime of previous i variable get 
26. over */

summary

1. initial value-garbage value
2. meomory location-stack (in every case meomory created in stack at compile time)
3. scope of variable-Local
4. lifetime of variable-Till control remain with that function

2)register -meomory create at compile time

-store in register and not in ram 

-for very fast access suppose you have make counter

1. #include <stdio.h>
2. #include <conio.h>
3. //register storage class ..very fast storage class use in cpu
4. 
   
5. int main()
6.    {
7.           
8.    reg int i;   
9.    
10.    if(i--)
11.    {
12.           printf("%d",i);
13.           main();
14. }
15.    
16.    
17.    
18.    getch();
19.    return 0;
20.           }

summary

-same summary as auto the only difference here accessing is through cpu rather than ram due to which it is a quick access

initial value-garbage value

memory location-stack

scope of variable-Local

lifetime of variable-Till control remain with that function

3)static-meomory create at runtime

1. #include <stdio.h>
2. #include <conio.h>
3. 
   
4.                                                               //no i outside
5. int main()
6.    {
7.           
8.    static int i=3;   
9.    
10.    if(i--)
11.    {
12.           printf("%d",i);
13.           main();
14. }
15.    
16.    
17.    
18.    getch();
19.    return 0;
20.           }

in above program your output will be 210 but now in above program if u don't write keyword static i.e if u write code

1. #include <stdio.h>
2. #include <conio.h>
3. 
   
4.                                                               
5. int main()
6.    {
7.           
8.    int i=3;   
9.    
10.    if(i--)
11.    {
12.           printf("%d",i);
13.           main();
14. }
15.    
16.    
17.    
18.    getch();
19.    return 0;
20.           }

then you will get 22222222........infinite times as in that case there will be just int which is auto storage class as we know . so, in this case meomory will be created at runtime .

IN COMPILER PROGRAM FIRST COMPILED THEN COMES ON RUNTIME

SO U CAN SAY STATIC NOT SUPPORT RECURSION

summary

1. initial value-0 and not garbage value
2. memory location-stack 
3. scope of variable-Local
4. lifetime of variable-Till control remain with that function

4)extern-meomory create at runtime

With this storage class you can access same common variable in any function all across program

1. #include <stdio.h>
2. #include <conio.h>
3. 
   
4. int i=3;                                                                  //i declare outside here
5. int main()
6.    {
7.           
8.    extern int i;   //this statement means don't create seprate meom for i here as i is already 
9.                          //created globally
10. //let if u write here i=5 then it will change i value all across program.   
11.    if(i--)
12.    {
13.           printf("%d",i);
14.           main();
15. }
16.    
17.    
18.    
19.    getch();
20.    return 0;
21.           }

HERE IN CASE IF U DON'T INITIALIZE YOUR VARIABLE GLOBALLY THEN U WILL GET AN ERROR.

summary

initial value-garbage value

memory location-stack

scope of variable-Local

lifetime of variable-Till control remain with that function