# C Puzzles

yet another place for C puzzles

## Big int implementation

a question from Microsoft.

Implement BigInt class (with +,-,*,-,^)

http://www.carljohansen.co.uk/bigint/
http://www.carljohansen.co.uk/bigint/BigInt.cs.txt

## subarray with largest sum

find the sum of contiguous subarray within a one-dimensional array of numbers which has the largest sum

http://geeksforgeeks.org/?p=576

## How do you reverse the words in a string?

`How do you reverse the words in a string?"My name is Yet Another Software Junk"to"Junk Software Another Yet is name My"answer:1. first reverse the string "My name is Yet Another Software Junk" to"knuJ erawtfoS rehtonA teY si eman yM"2. reverse word by word now"knuJ erawtfoS rehtonA teY si eman yM" to"Junk Software Another Yet is name My"`

## delete a node from circular singlely linked list with O(1)

`You are given a circular single linked list of sufficiently many number ofnodes(say more than 1 crore). You  need to delete a node say P and you aregiven a pointer to P in the circular single list.Suggest the most efficient methodology of deleting the node P from thecircular single linked list without rounding about the circular singlelinked list.Answer:`

We have a list looking like: ... -> Node(i-1) -> Node(i) -> Node(i+1) -> ... and we need to delete Node(i).

1. Copy data (not pointer, the data itself) from Node(i+1) to Node(i), the list will look like: ... -> Node(i-1) -> Node(i+1) -> Node(i+1) -> ...
2. delete the second Node(i+1), it doesn't require pointer to the previous node.

## Finding the Nth-node-from-the-end of a linked list.

1. travel the linked list for n times
(if you hit null in between, return null)
2. Then travel the linked list till end
(remember to increment the n-node pointer along with traversal)

Linked List B meet Linked List A at node J. find J

## sorted array right shfted

A sorted array . for eg: 2,3,6,8,11,23,56,89
It is right shifted unknown times eg: 23,56,89,2,3,6,8,11
now search an element in the array... say eg:56.
(no linear search allowed.)

1. first find the largest element by log(n)
2. now remove the first part or last part depends on search element.
3. now log(n) search for the item.

## queues with two stacks

implement queue with two stacks

## Big Endian or Little Endian

a c-program to find the endians of a processor?

unsigned int i = 0xabcdefgh;

unsigned char *pc = (unsigned char *) &i;

if (*pc == 0xgh) {
/* little endian */
} else {
/* big endian */
}

## compiler hack

Here is a C puzzle I(PCE) got from Bestin:

You have a magical program `a.c'. When you type `cc a.c', your compiler appears to hang (ie, you don't get back the prompt). Now,during this time, you will be able to type any program `b.c' in the standard input and type Ctrl-D. Once you do this, you get back the prompt. Now, you type `a.out' and magic, what you get will be the output of program `b.c'! Question is, what is this program `a.c'?

## curly bracket matching

Not a puzzle exactly.

Q. Are you familiar with curly bracket matching in vi editor?
(FYI: you may use % to find matching curly brackets)

implement this feature in 'your own' editor.

[you may even give a single-WORD-answer :-]

To simplify the question...
imagine a text with curly brackets like the following
"{{}{{}{}}{}}"

Input/output:
2nd curly matches with 3rd
1st curly with last one
4th with 9th

Now start writing the program.

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