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Reverse String
To reverse a string using stack operations - push() and pop()
Example:
s = "1234567890"
Traverse the string and push() all the char one by one to the stack till s will empty.
And
pop() all the char from stack, so we get our reversed string
"0987654321"
02. Count Consonants in String
Count Consonants in String
Given a string, count the number of consonants.
Note a consonant is a letter that is not a vowels,
i.e a letter that is not a,e,i,o, or u.
Example:
string_2 = "varaliya Mohammed"
Output:
9
Because there is 9 char present in the string which is consonent.
string_2 = "abc de"
Output:
3
Because there is 3 char present in the string which is consonent.
03. Look-and-Say Sequence
Look-and-Say Sequence
You have given a string - print the next look-and-say sequence
which means
if you have a string
"111221"
here
1 is read off as "one 1" or 11.
11 is read off as "two 1s" or 21.
21 is read off as "one 2, then one 1" or 1211.
1211 is read off as "one 1, one 2, then two 1s" or 111221.
111221 is read off as "three 1s, two 2s, then one 1" or 312211.
so the final string will be like this "312211"
04. String Processing: Spreadsheet Encoding
String Processing: Spreadsheet Encoding
ord("A") will return The ACII value which is 65
similarly
ord("B") is 67
String Processing: Is Palindrome
A palindrome is a word or phrase that is the same forward and backwards.
A phrase is a palindrome if, after converting all uppercase letters into lowercase letters and removing all non-alphanumeric characters, it reads the same forward and backward. Alphanumeric characters include letters and numbers.
s = "Was it a cat I saw?"# This is true
b = "Testing"# This is false
Given a string s, returntrueif it is a palindrome, or false otherwise.
Example 1:
Input: s = "A man, a plan, a canal: Panama"
Output: true
Explanation: "amanaplanacanalpanama" is a palindrome.
Example 2:
Input: s = "race a car"
Output: false
Explanation: "raceacar" is not a palindrome.
Example 3:
Input: s = ""
Output: true
Explanation: s is an empty string "" after removing non-alphanumeric characters.
Since an empty string reads the same forward and backward, it is a palindrome.
String Processing: Is Anagram
Anagram is a word or phrase that is made by arranging the letters of another word or phrase in a different order
Example:
below = elbow.
study = dusty.
night = thing.
Given two strings s and t, returntrueif t is an anagram of s, and false otherwise.
An Anagram is a word or phrase formed by rearranging the letters of a different word or phrase, typically using all the original letters exactly once.
Example 1:
Input: s = "anagram", t = "nagaram"
Output: true
Example 2:
Input: s = "rat", t = "car"
Output: false
07. String Processing: Is Palindrome Permutation
String Processing: Is Palindrome Permutation
Given a String, write a function to check if it is a permutation of a palindrome.
A palindrome is a word or phrase that is the same forward and backwards.
A permutation is a rearrangement of a letters. The palindrome does not need
to be limited to just dictionary words.
Example:
palin_perm = "Tact Coa" #Taco Cat
not_palin_perm = "This is not a palindrome permutation"
08. String Processing: Check Permutation
String Processing: Check Permutation
Given two strings, write a method to decide if
one is a prmutation of the other.
Example:
permutation example:
is_permutation_1 = "God"
is_permutation_2 = "dog"
no-permutation example:
not_permutation_1 = "Not"
not_permutation_2 = "got"
09. String Processing: Is Unique
String Processing: Is Unique
Implement an algorithm to determine if a string
has all unique characters.
Example:
unique_str_1 = 'ABCdefg'
non_unique_str_1 = 'non unique STR'
10. String Processing: Integer to String
String Processing: Integer to String
You are given some integer as input, (i.e. ... -3, -2, -1, 0, 1, 2, 3 ...)
Convert the integer you are given to a string.
Do not make use of the built-in "str" function.
Examples:
Input: 123
Output: "123"
Input: -123
Output: "-123"
String Processing: String to Integer
You are given some numeric string as input. Convert the string you are
given to an integer. Do not make use of the built-in "int" function.
Example:
"123": 123
"-12332": -12332
"554": 554
etc.
ord('0') = 48
ord('1') = 49
we want an integer 1 from given str '1', so
ord('1') - ord('0') = 1
like other integers,
ord('2') - ord('0') = 2
ord('3') - ord('0') = 3
ord('4') - ord('0') = 4
hence, we get our integers
String Processing: String to Integer (atoi)
Implement the myAtoi(string s) function, which converts a string to a 32-bit signed integer (similar to C/C++'s atoi function).The algorithm for myAtoi(string s) is as follows:Read in and ignore any leading whitespace.Check if the next character (if not already at the end of the string) is '-' or '+'. Read this character in if it is either. This determines if the final result is negative or positive respectively. Assume the result is positive if neither is present.Read in next the characters until the next non-digit character or the end of the input is reached. The rest of the string is ignored.Convert these digits into an integer (i.e. "123" -> 123, "0032" -> 32). If no digits were read, then the integer is 0. Change the sign as necessary (from step 2).If the integer is out of the 32-bit signed integer range [-231, 231 - 1], then clamp the integer so that it remains in the range. Specifically, integers less than -231 should be clamped to -231, and integers greater than 231 - 1 should be clamped to 231 - 1.Return the integer as the final result.Note: Only the space character '' is considered a whitespace character. Do not ignore any characters other than the leading whitespace or the rest of the string after the digits.Example 1: Input: s = "42" Output: 42 Explanation: The underlined characters are what is read in, the caret is the current reader position. Step 1: "42" (no characters read because there is no leading whitespace) ^ Step 2: "42" (no characters read because there is neither a '-' nor '+') ^ Step 3: "42" ("42" is read in) ^ The parsed integer is 42. Since 42 is in the range [-231, 231 - 1], the final result is 42.Example 2: Input: s = " -42" Output: -42 Explanation: Step 1: " -42" (leading whitespace is read and ignored) ^ Step 2: " -42" ('-' is read, so the result should be negative) ^ Step 3: " -42" ("42" is read in) ^ The parsed integer is -42. Since -42 is in the range [-231, 231 - 1], the final result is -42.Example 3: Input: s = "4193 with words" Output: 4193 Explanation: Step 1: "4193 with words" (no characters read because there is no leading whitespace) ^ Step 2: "4193 with words" (no characters read because there is neither a '-' nor '+') ^ Step 3: "4193 with words" ("4193" is read in; reading stops because the next character is a non-digit) ^ The parsed integer is 4193. Since 4193 is in the range [-231, 231 - 1], the final result is 4193.
12. Longest Substring Without Repeating Characters
Longest Substring Without Repeating Characters
Given a string s, find the length of the longest substring without repeating characters.
Example 1:
Input: s = "abcabcbb"
Output: 3
Explanation: The answer is "abc", with the length of 3.
Example 2:
Input: s = "bbbbb"
Output: 1
Explanation: The answer is "b", with the length of 1.
Example 3:
Input: s = "pwwkew"
Output: 3
Explanation: The answer is "wke", with the length of 3.
Notice that the answer must be a substring, "pwke" is a subsequence and not a substring.
Design an algorithm to encode a list of strings to a string. The encoded string is then sent over the network and is decoded back to the original list of strings.
Please implement encode and decode
Example
Example1:
Input: ["Hello","everyone","have","a", "great", "day"]
Output: ["Hello","everyone","have","a", "great", "day"]
Explanation:
One possible encode method is: "5#Hello8#everyone4#have1#a5#great3#day"
Example2:
Input: ["we", "say", ":", "yes"]
Output: ["we", "say", ":", "yes"]
Explanation:
One possible encode method is: "2#we3#say1#:3#yes"
You are given a string s and an integer k. You can choose any character of the string and change it to any other uppercase English character. You can perform this operation at most k times.
Return the length of the longest substring containing the same letter you can get after performing the above operations.
Example 1:
Input: s = "ABAB", k = 2
Output: 4
Explanation: Replace the two 'A's with two 'B's or vice versa.
Example 2:
Input: s = "AABABBA", k = 1
Output: 4
Explanation: Replace the one 'A'in the middle with 'B' and form "AABBBBA".
The substring "BBBB" has the longest repeating letters, which is 4.
There may exists other ways to achive this answer too.
Given two strings s and t of lengths m and n respectively, return the minimum window
substring of s such that every character in t (including duplicates) is included in the window. If there is no such substring, return the empty string "".
The testcases will be generated such that the answer is unique.
Example 1:
Input: s = "ADOBECODEBANC", t = "ABC"
Output: "BANC"
Explanation: The minimum window substring "BANC" includes 'A', 'B', and 'C' from string t.
Example 2:
Input: s = "a", t = "a"
Output: "a"
Explanation: The entire string s is the minimum window.
Example 3:
Input: s = "a", t = "aa"
Output: ""
Explanation: Both 'a's from t must be included in the window.
Since the largest window of s only has one 'a', return empty string.
Given a string s consisting of lowercase English letters, return the first letter to appear twice.
Note:
1. A letter a appears twice before another letter b if the second occurrence of a is before the second occurrence of b.
2. s will contain at least one letter that appears twice.
Example 1:
Input: s = "abccbaacz"
Output: "c"
Explanation:
The letter 'a' appears on the indexes 0, 5 and 6.
The letter 'b' appears on the indexes 1 and 4.
The letter 'c' appears on the indexes 2, 3 and 7.
The letter 'z' appears on the index 8.
The letter 'c' is the first letter to appear twice, because out of all the letters the index of its second occurrence is the smallest.
Example 2:
Input: s = "abcdd"
Output: "d"
Explanation:
The only letter that appears twice is 'd' so we return'd'.
Given a string s, find the first non-repeating character in it and return its index.
If it does not exist, return -1.
Example 1:
Input: s = "leetcode"
Output: 0
Example 2:
Input: s = "loveleetcode"
Output: 2
Example 3:
Input: s = "aabb"
Output: -1
18. Find the Index of the First Occurrence in a String
Given two strings needle and haystack, return the index of the first occurrence of `needle`in`haystack`,
or `-1`if`needle` is not part of `haystack`.
Example 1:
Input: haystack = "sadbutsad", needle = "sad"
Output: 0
Explanation: "sad" occurs at index 0 and 6.
The first occurrence is at index 0, so we return 0.
Example 2:
Input: haystack = "leetcode", needle = "leeto"
Output: -1
Explanation: "leeto" did not occur in"leetcode", so we return -1.