Misc

In infix expressions, the operator precedence is implicit unless we use parentheses. Therefore, for the infix to postfix conversion algorithm, we have to define the operator precedence inside the algorithm. We did this in the post covering infix, postfix and prefix expressions. What are infix, prefix and postfix expressions? Important properties:- Let us consider the infix expression 2 + 3 * 4 and its postfix will be 2 3 4 * +. Notice that between infix and postfix the order of the numbers(or operands) is unchanged. It is 2 3 …

Stacks can be used to check if the given expression has balanced symbols or not. The algorithm is very much useful in compilers. Each time parser reads one character at a time. If the character is an opening delimiter like ‘(‘ , ‘{‘ or ‘[‘ then it is PUSHED in to the stack. When a closing delimiter is encountered like ‘)’ , ‘}’ or ‘]’ is encountered, the stack is popped. The opening and closing delimiter are then compared. If they match, the parsing of the string continues. If they …

An implementation of stack is similar to that of a Linked List. We will try to discuss the basic operations in a stack discussed in this post. MAIN OPERATIONS ON A STACK:- push( int ) :- Inserts a data into the stack pop :- Returns the topmost data from the stack AUXILIARY OPERATIONS ON A STACK int Top( ) :- returns the topmost element on the stack int Size( ) :- returns the total size of the stack int isStackEmpty( ) :- returns true if the stack is empty The …

From Wikipedia: A segmentation fault occurs when a program attempts to access a memory location that it is not allowed to access, or attempts to access a memory location in a way that is not allowed (for example, attempting to write to a read-only location, or to overwrite part of the operating system). Segmentation is one approach to memory management and protection in the operating system. It has been superseded by paging for most purposes, but much of the terminology of segmentation is still used, “segmentation fault” being an example. …

This is one of the method, not everyone is aware of in C. To generate a random number, C itself provides us a method srand(). We can use it in this way. NOTE: The function srand(time(NULL)) can only be called once in the program.

Many of us must have heard of the clause “Real Programmers code in C” and it is faster than any other language because “it is close to the machine“. What is so special about this language that makes it different from any other language. Let us try to explore this answer to some extent. There isn’t much that’s special about C. That’s one of the reasons why it’s fast. Newer languages which have support for garbage collection, dynamic typing and other facilities which make it easier for the programmer to …

Question: Write a program to reverse a Linked List in pairs. That means we should reverse the 1st and 2nd numbers, 3rd and 4th numbers and so on. Input: 4, 8, 15, 16, 23, 42 Output: 8, 4, 16, 15, 42, 23 The basic idea behind solving this problem is that we need to traverse the entire list and we need to keep on swapping the values of 2 adjacent nodes. Since we need to reverse the values in pairs, it is also clear that we need to move 2 …

Question: In C you can do something like:- char s[] = “Hello World”; and char *s = “Hello World”; What is the difference between the two of them? What happens to the memory during compile time and run-time? This declaration: Creates ONE object – a char array of size 6, called s, initialized with the values ‘h’, ‘e’, ‘l’, ‘l’, ‘o’, ‘\0’. Where this array is allocated in memory, and how long it lives for, depends on where the declaration appears. If the declaration is within a function, it will …

Question: C does not have the boolean data type by default. Is there a way by which we can implement it? In C language, we do not have the boolean datatype by default. That means we cannot do something like We can do this in C++ and JAVA. However, we have an alternative method to achieve the same functionality. Before moving on to the implementation it is important to know that in C, if a value is ‘0 (zero)’ it is treated as false, and any other value other than …

Question: What is the difference between doing:         ptr = (char **) malloc (MAXELEMS * sizeof(char *)); or:         ptr = (char **) calloc (MAXELEMS, sizeof(char*)); When is it a good idea to use calloc and when to use malloc ? There are two differences:- Firstly it is in the number of arguments, malloc() takes a single argument (memory required in bytes), while calloc() needs two arguments. Secondly, malloc() does not initialize the memory allocated, while calloc() initializes the allocated memory to ZERO. calloc() allocates a memory area, the length …