String

Uncommon Words from Two Sentences Problem

Problem A sentence is a string of single-space separated words where each word consists only of lowercase letters. A word is uncommon if it appears exactly once in one of the sentences, and does not appear in the other sentence. Given two sentences s1 and s2, return a list of all the uncommon words. You may return the answer in any order. Examples Example 1: ...

Find the Longest Substring Containing Vowels in Even Counts Problem

Problem Given the string s, return the size of the longest substring containing each vowel an even number of times. That is, ‘a’, ’e’, ‘i’, ‘o’, and ‘u’ must appear an even number of times. Examples Example 1: Input: s = "eleetminicoworoep" Output: 13 Explanation: The longest substring is "leetminicowor" which contains two each of the vowels: e, i and o and zero of the vowels: a and u. ...

Sum of Digits of String After Convert Problem

Problem You are given a string s consisting of lowercase English letters, and an integer k. First, convert s into an integer by replacing each letter with its position in the alphabet (i.e., replace 'a' with 1, 'b' with 2, …, 'z' with 26). Then, transform the integer by replacing it with the sum of its digits. Repeat the transform operation k times in total. For example, if s = "zbax" and k = 2, then the resulting integer would be 8 by the following operations: ...

Number of Senior Citizens Problem

Problem You are given a 0-indexed array of strings details. Each element of details provides information about a given passenger compressed into a string of length 15. The system is such that: The first ten characters consist of the phone number of passengers. The next character denotes the gender of the person. The following two characters are used to indicate the age of the person. The last two characters determine the seat allotted to that person. Return the number of passengers who are strictly more than 60 years old. ...

Minimum Deletions to Make String Balanced Problem

Problem You are given a string s consisting only of characters 'a' and 'b'. You can delete any number of characters in s to make s balanced. s is balanced if there is no pair of indices (i,j) such that i < j and s[i] = 'b' and s[j]= 'a'. Return the minimum number of deletions needed to make s balanced. Examples Example 1: Input: s = "aababbab" Output: 2 Explanation: You can either: Delete the characters at 0-indexed positions 2 and 6 ("aa{b}abb{a}b" -> "aaabbb"), or Delete the characters at 0-i ndexed positions 3 and 6 ("aab{a}bb{a}b" -> "aabbbb"). ...

Reverse words in a string keep delimiters in order

Problem Given a string and a set of delimiters, reverse the words in the string while maintaining the relative order of the delimiters. For example, given “hello/world:here”, return “here/world:hello” Follow-up Does your solution work for the following cases: "hello/world:here/", "hello//world:here" Examples Example 1: Input: s = hello/world:here Output: here/world:hello Solution Method 1 - Using stack to store words and queue for delimiters Code Java class Solution { public String reverseWords(String s) { Stack<String> stack = new Stack<>(); Queue<String> queue = new LinkedList<>(); StringBuilder word = new StringBuilder(); int i = 0; while (i < s.length()) { char c = s.charAt(i); if (Character.isLetterOrDigit(c)) { word.append(c); i++; } else { if (word.length() > 0) { stack.push(word.toString()); } word = new StringBuilder(); // clear word for next word StringBuilder delim = new StringBuilder(); delim.append(c); i++; // tracking continuous delimiter to add to queue while (i < s.length() && !Character.isLetterOrDigit(s.charAt(i))) { delim.append(c); i++; } queue.add(delim.toString()); } } // if string ends with words if (word.length() != 0) { stack.push(word.toString()); } boolean isWordFirst = Character.isLetterOrDigit(s.charAt(0)); StringBuilder sb = new StringBuilder(); // if word is not first, add 1 entry from queue if (!isWordFirst) { if (!queue.isEmpty()) { sb.append(queue.remove()); } } // now put 1 element from either till not empty while (!stack.isEmpty() || !queue.isEmpty()) { if (!stack.isEmpty()) { sb.append(stack.pop()); } if (!queue.isEmpty()) { sb.append(queue.remove()); } } return sb.toString(); } } ...

Largest Positive Integer That Exists With Its Negative

Problem Given an integer array nums that does not contain any zeros, find the largest positive integer k such that -k also exists in the array. Return the positive integer k. If there is no such integer, return -1. Examples Example 1: Input: nums = [-1,2,-3,3] Output: 3 Explanation: 3 is the only valid k we can find in the array. ...

Reverse Prefix of Word

2Sum Problem Problem Given a 0-indexed string word and a character ch, reverse the segment of word that starts at index 0 and ends at the index of the first occurrence of ch (inclusive). If the character ch does not exist in word, do nothing. For example, if word = "abcdefd" and ch = "d", then you should reverse the segment that starts at 0 and ends at 3 (inclusive). The resulting string will be "dcbaefd". Return the resulting string. ...

Buddy Strings Problem

Problem Given two strings s and goal, return true if you can swap two letters in s so the result is equal to goal, otherwise, return false. Swapping letters is defined as taking two indices i and j (0-indexed) such that i != j and swapping the characters at s[i] and s[j]. For example, swapping at indices 0 and 2 in "abcd" results in "cbad". Examples Example 1: ...

Find the Closest Palindrome Problem

Problem Given a string n representing an integer, return the closest integer (not including itself), which is a palindrome. If there is a tie, return the smaller one. The closest is defined as the absolute difference minimized between two integers. Examples Example 1: Input: n = "123" Output: "121" Example 2: Input: n = "1" Output: "0" Explanation: 0 and 2 are the closest palindromes but we return the smallest which is 0. ...