SDE - 1

You have been given a non-empty grid consisting of only 0s and 1s. You have to find the number of islands in the given grid.

An island is a group of 1s (representing land) connected horizontally, vertically or diagonally. You can assume that all four edges of the grid are surrounded by 0s (representing water).

Ninjas is practicing problems on the linked list. He came across a problem in which he has given a linked list of ‘N’ nodes and two integers, ‘LOW’ and ‘HIGH’. He has to return the linked list ‘HEAD’ after reversing the nodes between ‘LOW’ and ‘HIGH’, including the nodes at positions ‘LOW’ and ‘HIGH’.

You have been given a Snake and Ladder Board with 'N' rows and 'N' columns with the numbers written from 1 to (N*N) starting from the bottom left of the board, and alternating direction each row.

For example

For a (6 x 6) board, the numbers are written as follows:

You start from square 1 of the board (which is always in the last row and first column). On each square say 'X', you can throw a dice which can have six outcomes and you have total control over the outcome of dice throw and you want to find out the minimum number of throws required to reach the last cell.
Some of the squares contain Snakes and Ladders, and these are possibilities of a throw at square 'X':
You choose a destination square 'S' with number 'X+1', 'X+2', 'X+3', 'X+4', 'X+5', or 'X+6', provided this number is <= N*N.
If 'S' has a snake or ladder, you move to the destination of that snake or ladder.  Otherwise, you move to S.
A board square on row 'i' and column 'j' has a "Snake or Ladder" if board[i][j] != -1. The destination of that snake or ladder is board[i][j].

Note :

You can only take a snake or ladder at most once per move: if the destination to a snake or ladder is the start of another snake or ladder, you do not continue moving - you have to ignore the snake or ladder present on that square.

For example, if the board is:
-1 1 -1
-1 -1 9
-1 4 -1
Let's say on the first move your destination square is 2  [at row 2, column 1], then you finish your first move at 4 [at row 1, column 2] because you do not continue moving to 9 [at row 0, column 0] by taking the ladder from 4.

A square can also have a Snake or Ladder which will end at the same cell.
For example, if the board is:
-1 3 -1
-1 5 -1
-1 -1 9
Here we can see Snake/Ladder on square 5 [at row 1, column 1] will end on the same square 5.

You are given 2 non-empty strings 's1' and 's2' consisting of lowercase English alphabets only.

In one operation you can do either of the following on 's1':

(1) Remove a character from any position in 's1'.

(2) Add a character to any position in 's1'.

Find the minimum number of operations required to convert string 's1' into 's2'.

Example:

Input: 's1' = "abcd", 's2' = "anc"

Output: 3

Explanation:
Here, 's1' = "abcd", 's2' = "anc".
In one operation remove 's1[3]', after this operation 's1' becomes "abc".    
In the second operation remove 's1[1]', after this operation 's1' becomes "ac".
In the third operation add 'n' in 's1[1]', after this operation 's1' becomes "anc".

Hence, the minimum operations required will be 3. It can be shown that there's no way to convert s1 into s2 in less than 3 moves.

You are given the text ‘IPAddress’. Your task is to check if the given text ‘IPAddress’ is a valid ‘IPv4’ or not.

Conditions for a valid ‘IPv4’ are:

1. Text form of ‘IPAddress’ must be ‘a.b.c.d’
2. The values of a,b,c and d can vary from ‘0’ to ‘255’ and both ‘0’ and ‘255’ are inclusive.