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[LeetCode 217] Contains Duplicate

Problem

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.

Example 1:

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

Example 2:

Input: nums = [1,2,3,4]
Output: false

Example 3:

Input: nums = [1,1,1,3,3,4,3,2,4,2]
Output: true

Constraints:

  • 1 <= nums.length <= 10^5
  • -10^9 <= nums[i] <= 10^9

Thoughts

  • We can use Set to check for existence

TypeScript

function containsDuplicate(nums: number[]): boolean {
    const s: Set<number> = new Set<number>();
    
    for(let num of nums){
        if(s.has(num)) return true
        else s.add(num)
    }
    
    return false;
};

Reference