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51 leetcode.com Number of Segments in a String Problem Solving Very easy Given a string s, return the number of segments in the string. A segment is defined to be a contiguous sequence of non-space characters.   Example 1: Input: s = "Hello, my name is John" Output: 5 Explanation: The five segments are ["Hello,", "my", "name", "is", "John"] Example 2: Input: s = "Hello" Output: 1
49 leetcode.com Add Strings Problem Solving Medium Given two non-negative integers, num1 and num2 represented as string, return the sum of num1 and num2 as a string. You must solve the problem without using any built-in library for handling large integers (such as BigInteger). You must also not convert the inputs to integers directly.   Example 1: Input: num1 = "11", num2 = "123" Output: "134" Example 2: Input: num1 = "456", num2 = "77" Output: "533" Example 3: Input: num1 = "0", num2 = "0" Output: "0"
48 leetcode.com Valid Perfect Square Problem Solving Easy Given a positive integer num, write a function which returns True if num is a perfect square else False. Follow up: Do not use any built-in library function such as sqrt.   Example 1: Input: num = 16 Output: true Example 2: Input: num = 14 Output: false
46 leetcode.com Nim Game Problem Solving Easy You are playing the following Nim Game with your friend: Initially, there is a heap of stones on the table. You and your friend will alternate taking turns, and you go first. On each turn, the person whose turn it is will remove 1 to 3 stones from the heap. The one who removes the last stone is the winner. Given n, the number of stones in the heap, return true if you can win the game assuming both you and your friend play optimally, otherwise return false.   Example 1: Input: n = 4 Output: false Explanation: These are the possible outcomes: 1. You remove 1 stone. Your friend removes 3 stones, including the last stone. Your friend wins. 2. You remove 2 stones. Your friend removes 2 stones, including the last stone. Your friend wins. 3. You remove 3 stones. Your friend removes the last stone. Your friend wins. In all outcomes, your friend wins. Example 2: Input: n = 1 Output: true Example 3: Input: n = 2 Output: true
45 leetcode.com Valid Anagram Problem Solving Easy Given two strings s and t, return true if 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
44 leetcode.com Power of Two Problem Solving Easy Given an integer n, return true if it is a power of two. Otherwise, return false. An integer n is a power of two, if there exists an integer x such that n == 2x.   Example 1: Input: n = 1 Output: true Explanation: 20 = 1 Example 2: Input: n = 16 Output: true Explanation: 24 = 16 Example 3: Input: n = 3 Output: false
43 leetcode.com Word Pattern Problem Solving Medium Given a pattern and a string s, find if s follows the same pattern. Here follow means a full match, such that there is a bijection between a letter in pattern and a non-empty word in s.   Example 1: Input: pattern = "abba", s = "dog cat cat dog" Output: true Example 2: Input: pattern = "abba", s = "dog cat cat fish" Output: false Example 3: Input: pattern = "aaaa", s = "dog cat cat dog" Output: false
42 leetcode.com Isomorphic Strings Problem Solving Medium Given two strings s and t, determine if they are isomorphic. 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: Input: s = "egg", t = "add" Output: true Example 2: Input: s = "foo", t = "bar" Output: false Example 3: Input: s = "paper", t = "title" Output: true
41 leetcode.com First Unique Character in a String Problem Solving Easy 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
40 leetcode.com Find the Difference Problem Solving Medium You are given two strings s and t. String t is generated by random shuffling string s and then add one more letter at a random position. Return the letter that was added to t.   Example 1: Input: s = "abcd", t = "abcde" Output: "e" Explanation: 'e' is the letter that was added. Example 2: Input: s = "", t = "y" Output: "y"
Results: 180