Evaluation of POSTFIX expression using STACK

Evaluation of POSTFIX expression using STACK :

To evaluation the value of a POSTFIX expression STACK can be used in the following way:
Procedure: Add #, a pound symbol, a sentinel, a terminating symbol at the end of the POSTFIX expression. Scan the expression from left to right till #.If the character scanned character is an operand PUSH it on to STACK. If the scanned character is any operator, * , POP STACK once call it B and POP again and call it A, find A * B, and PUSH the result on to STACK. If the character scanned is #, then POP the STACK and it is the value of the POSTFIX expression.. For example consider a POSTFIX expression, 6 3 2| *3 6 +/.

The value of POSTFIX expression is 6.
Algorithm to evaluate the value of POSTFIX expression:
POSTFIXVAL (P)
[P is a POSTFIX expression]
Add # at the end of P
Repeat Scanning P from left to right While scanned character
< > #
If Scanned Character = operand Then:
[PUSH it on to STACK]
STACK [TOP]<--OPERAND, TOP<--TOP+1
Else:
B<--STACK[TOP], TOP<--TOP-1
A<--STACK[TOP],TOP<--TOP-1
RES <-- A operator B
STACK [TOP]<--RES
[End of While]
VAL<--STACK[TOP]
Write : ‘Value of POSTFIX expression is ‘, VAL
Exit.

Comments

difference between structure and union in C Language

In c language article we will see the difference between union and structure. Both are the user define datatype in c language. See the table which is mentioned below: ASP.NET Video Tutorial Series Structure Union1.The keywordstruct is used to define a structure 1. The keyword union is used to define a union. 2. When a variable is associated with a structure, the compiler allocates the memory for each member. The size of structure is greater than or equal to the sum ofsizes of its members. The smaller members may end with unused slack bytes. 2. When a variable is associated with a union, thecompiler allocates thememory by considering the size of the largest memory. So, size of union is equal to the size of largest member. 3. Each member within a structure is assigned unique storage area of location. 3. Memory allocated is shared by individual members of union. 4. The address of each member will be in ascending order This indicates that memory for each member will start at different offset v…

Difference between Linear search and Binary Search in c language

SQL Video Channel : Download all SQL Video

Binary Search Linear Search Works only on sorted items. such as 1,2,3,4,5,6 etc
Works on sorted as well as unsorted items. 12,4,5,3,2,1 etc Very efficient if the items are sorted Very efficient if the items are less and present in the beginning of the list. such as Suppose your list items are : 12,3,4,5,1 and you want to search 12 number then you get beginning in the list. Works well with arrays and not on linked lists. Works with arrays and linked lists.
Number of comparisons are less More number of comparisons are required if the items are present in the later part of the array or its elements are more.

Memory representation of Linked List Data Structures in C Language

Memory representation of Linked List

In memory the linked list is stored in scattered cells (locations).The memory for each node is allocated dynamically means as and when required. So the Linked List can increase as per the user wish and the size is not fixed, it can vary.

Suppose first node of linked list is allocated with an address 1008. Its graphical representation looks like the figure shown below:

Suppose next node is allocated at an address 506, so the list becomes,

Suppose next node is allocated with an address with an address 10,s the list become,

The other way to represent the linked list is as shown below:

In the above representation the data stored in the linked list is “INDIA”, the information part of each node contains one character. The external pointer root points to first node’s address 1005. The link part of the node containing information I contains 1007, the address of next node. The last node …

Computer Programming

Search This Blog