Stack
A stack is a basic data structure that can be logically thought as linear structure represented by a real physical stack or pile,a structure where insertion and deletion of items takes place at one end called top of the stack.(Last In First Out)
Deletion from Stack Array
Deletion Stack Array (Pop operation)
1. Function Stack_pop(top , array[])
2. if( top==0 )
3. print( “Underflow” );
4. return
5. end if
6. top--
7. end Stack_pop
Time Complexity :- O(1)
Deletion from Stack List
Deletion Stack List (Pop operation)
1. Function Stack_pop(top , START , list)
2. if( START == NULL )
3. print( “Underflow” );
4. return
5. end if
6. ptr = START
7. while( ptr.NEXT != top )
8. ptr = ptr.NEXT
9. end while
10. ptr = top
11. temp = ptr.NEXT
12. delete(temp)
13. end Stack_pop
Time Complexity :- O(n)
Stack Insertion Array
Stack insertion Array (Push operation)
1. Function Stack_push (top , array[] , max , num) //num is the value to be inserted
2. if( top == max )
3. print(“overflow”)
4. return
5. end if
6. top++
7. a[top] = num
8. end Stack_push
Time Complexity :- O(1)
Stack Insertion List
Stack insertion List (Push operation)
1. Function Stack_push (top , list , num) //num is the value to be inserted
2. new_node = new list // allocating memory to new node of list
3. top.NEXT = new_node
4. top = new_node
5. end Stack_push
Time Complexity :- O(1)
Stack Traverse Array
Stack traverse Array (Peep operation)
1. Function peep( array[] , top )
2. if( top == 0 )
3. print( “Underflow” )
4. return
5. end if
6. ptr = top
7. while(ptr != 0 )
8. print( “array[ptr]” )
9. ptr--
10. end while
11. end peep
Time Complexity :- O(n)
Stack Traverse List
Stack traverse List (Peep operation)
1. Function peep( list , top )
2. if( top == NULL )
3. print( “Underflow” )
4. return
5. end if
6. ptr = top
7. while(ptr.NEXT != NULL )
8. print( “ptr.data” )
9. ptr = ptr.NEXT
10. end while
11. end peep
Time Complexity :- O(n)
