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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 <= 105
  • -109 <= nums[i] <= 109

Solution​

/**
 * @param {number[]} nums
 * @return {boolean}
 */
var containsDuplicate = function(nums) {
    const map = {};
    for (const n of nums) {
        if (n in map) {
            return true;
        }
        map[n] = true;
    }
    return false;
};

Use a hashmap map to test whether a value appears more than once in nums.