Contains Duplicate

LeetCode: https://leetcode.com/problems/contains-duplicate/

Given an integer array nums, return true if any value appears at least twice, and false if every element is distinct.

Example:

Input: nums = [1,2,3,1]
Output: true

1def containsDuplicate(nums: List[int]) -> bool:
2    seen = set()
3    
4    for x in nums:
5        if x in seen:
6            return True
7        seen.add(x)
8        
9    return False

Two Sum

Valid Anagram

Step 1 / 4

Step 1:

seen is empty. Read 1, add it to seen.

Pointers: i=0

Focus: select @ [0]