2. LeetCode Success: Follow This Easy Step-by-Step Guide

Open the Problem on LeetCode:

• Navigate to the problem on LeetCode, such as "Contains Duplicate."

Understand the Problem Statement:

• Read the problem description carefully.

• For example, in "Contains Duplicate," the question states:
  "Given an integer array nums, return true if any value appears at least twice in the array, and return false if every element is distinct."

• Simplify this in your own words:

  • "We are given an integer array called nums. We need to check if the array contains any duplicate values. If it does, return true; otherwise, return false."

Examine the Examples for Clarity:

• Look at the examples provided in the problem to better understand the requirement:

  • Example 1:

    • Input: nums = [1, 2, 3, 1]

    • Output: true

    • Explanation: The number 1 appears twice, at indices 0 and 3.

  • Based on this example, you understand that the task is to find duplicates and return true if duplicates exist; otherwise, return false.

Analyze the Constraints:

• Review the constraints to determine the input size and range of values:

  • Example Constraints:

    • 1 <= nums.length <= 10^5: The array can contain up to 100,000 elements.

    • -10^9 <= nums[i] <= 10^9: Each element in the array is within the range of -1 billion to 1 billion.

• Use these constraints to decide:

  • Should you write a brute-force solution or aim for an optimized approach?

  • Since the array size can go up to 1 lakh, a brute-force O(n2)O(n^2)O(n2) solution will exceed the time limit. Therefore, you should aim for an O(n)O(n)O(n) or O(nlog⁡n)O(n \log n)O(nlogn) solution.

Plan the Solution:

• Now that you understand the problem, examples, and constraints:

  • Think of a clear plan or algorithm to solve the problem efficiently.

  • For this example:

    • Use a HashSet to track numbers you've seen before. If you encounter a number that's already in the set, return true. If you finish checking the array without finding duplicates, return false.

Write and Test Your Code:

• Write the code for your solution.

• Test it against the provided examples and edge cases to ensure it works correctly.