leetcode/work/Easy/Array/217.contains-duplicate.js

/*
 * 217. Contains Duplicate
 * Difficulty: Easy
 * https://leetcode.com/problems/contains-duplicate/
 * 
 * ──────────────────────────────────────────────────
 * 
 * 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
 * 
 * Explanation:
 * 
 * The element 1 occurs at the indices 0 and 3.
 * 
 * Example 2:
 * 
 * Input: nums = [1,2,3,4]
 * 
 * Output: false
 * 
 * Explanation:
 * 
 * All elements are distinct.
 * 
 * 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
*/

/**
 * @param {number[]} nums
 * @return {boolean}
 */
var containsDuplicate = function(nums) {
  const freq = {};
  for (let n of nums) {
    freq[n] = (freq[n] || 0) + 1;
    if (freq[n] >= 2) {
      return true;
    }
  } 
  return false;
};