srm707 easy Cross
problem
There is a rectangular board that is divided into n rows by m columns of cells. Each cell is either black or white. You are given the description of the board in the board. Each character in board represents one cell. More precisely, the character board[i][j] represents the cell at coordinates (row i, column j). The character ‘#’ represents a black cell, the character ‘.’ is a white cell. Formally, there is a cross centered at (x, y) if the following five cells are all black: (x, y), (x+1, y), (x-1, y), (x, y-1), and (x, y+1). Note that other cells adjacent to the cross may also be black, it is still a valid cross.
Return “Exists” if there is at least one cross on the given board. Otherwise, return “Does not exist”. Note that the return value is case-sensitive.
code
Delete Middle Node
problem
Implment an algorithm to delete a node in the middle of a singly linked list. But you can only access to that node.
note
The solution is simply to copy the data from the next node over to the current node.
code
RemoveDups
problem
Write code to remove duplicates from an unsorted linked list without using a temporary buffer.
how to solve
If I can use a temporary buffer, I recommend to use hash table. But in this case, I have to compare two elements to check that they are duplicated or not by using brute force search.
code
Insertion
problem
You are given two 32bit numbers n and m and two bit positions, i and j. Write a method to insert M into N such that M starts at bit j and ends at bit i.
how to solve
- Clear the bits j through i in N
- Shift M so that it lines up with bits j through i
- Merge M and N
code
AnimalShelter
Problem
An animal shelter, which holds only dogs and cats. Create the data structures to implement operations such as enqueue, dequeueAny, dequeueDog and dequeueCat.
How to solve
My approach is to simply use separate queues for dogs and cats. Then we store some sort of timestamp to mark when each animal was enqueued. When we called dequeueAny, we compare the front of the dog and cat queue and return the oldest.
Code
Rotate Matrix
problem
Given an image represented by an N*N matrix, where each pixel in the image is 4 bytes, write a method to rotate the image by 90 degrees. Can you do this in place?
how to solve
We swap on each layer, starting from the outermost layer and working our way inwards.
code
OneAway
Problem
There are three types of edits that can be performed on strings: insert a character, remove a character, or replace a character. Given two strings, write a function to check if they are one edit (or zero edits) away.
How to solve
Implement three method testing whether the array can be edited by each way. I can check the possibility of each edit by the following way.
Insert and Remove This means if we compared the strings they would be identical except for one character and the difference of the length is one.
Replace This means that two strings are different only in one place
