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Given an integer array nums, determine if it contains any duplicates. Return true if any value appears at least twice in the array, and return false if every element is distinct. Constraints: 1 <= nums.length <= 10^5 10^9 <= nums[i] <= 10^9 Example: Input: nums = [1,2,3,1] Output: true Explanation:
Given an input string s, reverse the order of the words. Constraints: A word is defined as a sequence of nonspace characters. Words are separated by at least one space. The input string may contain leading or trailing spaces. Multiple spaces between two words should be reduced to a single space in t
You are given an array nums containing n distinct numbers in the range [0, n]. Your task is to find and return the only number in the range that is missing from the array. n is the length of nums. 1 <= n <= 10^4 0 <= nums[i] <= n All numbers in nums are unique. Example 1: Input: nums = [3,0,1] Outpu
A palindrome is a sequence of characters that reads the same forwards and backwards. Given a string s, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases. For example: Input: s = "A man, a plan, a canal: Panama" Output: true Explanation: "amanaplanacanalpana
Given a string s containing just the characters (, ), {, }, [, ], determine if the input string is valid. A string is valid if: Open brackets must be closed by the same type of brackets. Open brackets must be closed in the correct order. Every close bracket has a corresponding open bracket of the sa
Given an integer array nums, rotate the array to the right by k steps, where k is nonnegative. You must do this inplace with O(1) extra space. Constraints: 1 <= nums.length <= 10^5 2^31 <= nums[i] <= 2^31 1 0 <= k <= 10^5 Example: Input: nums = [1,2,3,4,5,6,7], k = 3 Output: [5,6,7,1,2,3,4] Explanat
Given a string s, find the first nonrepeating character in it and return its index. If it does not exist, return 1.The string s consists of only lowercase English letters.
A practical step-by-step framework for approaching any DSA interview question, from clarifying requirements to testing edge cases.
Explains the time-space tradeoff using memoization and hash tables as examples, with guidance on which resource to prioritize.
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