# String

String DSA Question Swift

## Count number of substrings with exactly k distinct characters

[Question]: You are given a string ‘str’ of lowercase alphabets and an integer’k’ .Your task is to return the count all the possible substrings that have exactly ‘k’ distinct characters.For example:‘str’ = abcad and ‘k’ = 2.We can see that the substrings {ab, bc, ca, ad} are the only substrings with 2 distinct characters. Therefore, …

## String to Integer conversion (atoi)

[Question]: Convert given string into Integer with given condition Approach #2 Using Recursion Plain Atoi Solution

## Roman to Int conversion

[Question]: Convert Roman number into Int, Roman numerals are represented by seven different symbols: I, V, X, L, C, D and M. Symbol Value I 1 V 5 X 10 L 50 C 100 D 500 M 1000 Example III = 3 IV = 4

## Maximum Nesting Depth of the Parentheses

[Question]: In a given string find maximum depth of parentheses. input string has only “( )” type parenthesesExample: Input = “(1+(5*8)+((9)/2))+100” || Output = 2

## Sort Characters By Frequency

[Questions]: Given a string s, sort it in decreasing order based on the frequency of the characters. for example “tree” so ee has highest appearance hence answer will be eert Return the sorted string. If there are multiple answers, return any of themInput: s = “tree”Output: “eert”

## How to find Longest Common Prefix in strings Array

[Question]: In a given string array find the longest common prefix Example: Input [“fl”,”flower”,”flight”]Output: “fl”// because this is common prefix in the given string. #Approach Binary search We will create two pointers low & high, low starts from 0 & high is first object count. so now we will divide string into two parts and …

## How to check Isomorphic Strings?

[Question]: Given two strings s and t, determine if they are isomorphic. Definition: Two strings s and t are isomorphic if the characters in s can be replaced to get t. All occurrences of a character must be replaced with another character while preserving the order of characters. No two characters may map to the same character, but a character may map to itself. Example 1: …

## Check if two strings are anagrams

[Question]: Given two string check weather they anagramExample: abc & cab are anagram Approach #2 Using Hash map / Dictionary Approach #3:  Using reduce function.

## Check if string is rotated

[Question]: Given two strings s and goal, return true if and only if s can become goal after some number of shifts on s. A shift on s consists of moving the leftmost character of s to the rightmost position. For example, if s = “abcde”, then it will be “bcdea” after one shift. Input: s = “abcde”, goal = “abced” Output: false

## Find largest odd Number/Sequence in String

[Question]: In integer string Return the largest-valued odd integer (as a string) that is a non-empty substring of num, or an empty string “” if no odd integer exists. A substring is a contiguous sequence of characters within a string. Example 1: Input: num = “52” Output: “5” Explanation: The only non-empty substrings are “5”, “2”, and “52”. “5” is the only odd number input …