# DSA Day-3

Hello Guys!! Hope you are safe and working hard for upcoming placement and exam season.

Since, Microsoft is coming on my college campus, my juniors requested me to include microsoft asked questions daily till the selection procedure ends.

So, here I am with a bunch of questions on strings.

I understand that you all are busy with exams but the company is visiting coming week and it is one of the best companies.

I can only light up the path for you… you have to walk on it on your own. So, pull up your socks and get ready to work harder than before. I’ve included links for practice on this post.

Just few questions, take out time and solve these questions.

1. Implement `atoi` which converts a string to an integer.

The function first discards as many whitespace characters as necessary until the first non-whitespace character is found. Then, starting from this character, takes an optional initial plus or minus sign followed by as many numerical digits as possible, and interprets them as a numerical value.

The string can contain additional characters after those that form the integral number, which are ignored and have no effect on the behavior of this function.

If the first sequence of non-whitespace characters in str is not a valid integral number, or if no such sequence exists because either str is empty or it contains only whitespace characters, no conversion is performed.

If no valid conversion could be performed, a zero value is returned.

Note:

• Only the space character `' '` is considered as whitespace character.
• Assume we are dealing with an environment which could only store integers within the 32-bit signed integer range: [−231, 231 − 1]. If the numerical value is out of the range of representable values, INT_MAX (231 − 1) or INT_MIN (−231) is returned.

Example 1:

`Input: "42"Output: 42`

Example 2:

`Input: "   -42"Output: -42Explanation: The first non-whitespace character is '-', which is the minus sign.             Then take as many numerical digits as possible, which gets 42.`

Example 3:

`Input: "4193 with words"Output: 4193Explanation: Conversion stops at digit '3' as the next character is not a numerical digit.`

Example 4:

`Input: "words and 987"Output: 0Explanation: The first non-whitespace character is 'w', which is not a numerical              digit or a +/- sign. Therefore no valid conversion could be performed.`

2. Write a function that reverses a string. The input string is given as an array of characters `char[]`.

Do not allocate extra space for another array, you must do this by modifying the input array in-place with O(1) extra memory.

You may assume all the characters consist of printable ascii characters.

Example 1:

`Input: ["h","e","l","l","o"]Output: ["o","l","l","e","h"]`

Example 2:

`Input: ["H","a","n","n","a","h"]Output: ["h","a","n","n","a","H"]`

3. Given an input string, reverse the string word by word.

Example 1:

`Input: "the sky is blue"Output: "blue is sky the"`

Example 2:

`Input: "  hello world!  "Output: "world! hello"Explanation: Your reversed string should not contain leading or trailing spaces.`

Example 3:

`Input: "a good   example"Output: "example good a"Explanation: You need to reduce multiple spaces between two words to a single space in the reversed string.`

Note:

• A word is defined as a sequence of non-space characters.
• Input string may contain leading or trailing spaces. However, your reversed string should not contain leading or trailing spaces.
• You need to reduce multiple spaces between two words to a single space in the reversed string.

4. Given an input string , reverse the string word by word.

Example:

`Input:  ["t","h","e"," ","s","k","y"," ","i","s"," ","b","l","u","e"]Output: ["b","l","u","e"," ","i","s"," ","s","k","y"," ","t","h","e"]`

Note:

• A word is defined as a sequence of non-space characters.
• The input string does not contain leading or trailing spaces.
• The words are always separated by a single space.

Follow up: Could you do it in-place without allocating extra space?

Upcoming Post: Previous to previous year Microsoft selection procedure(it keeps on changing, so yeah) , DSA Day-4

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## Arya Goswami

177 Followers

Incoming SDE intern at Amazon || Ex- mentee at Amazon ACMS