Contains Duplicate

Given an array of integers, find if the array contains any duplicates.

Your function should return true if any value appears at least twice in the array, and it should return false if every element is distinct.

Example 1:

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

Example 2:

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

Example 3:

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

Solution:

/**
 * @param {number[]} nums
 * @return {boolean}
 */
var containsDuplicate = function (nums) {
    let result = false;
    let p1 = 0;
    let p2 = 0;
    let len = nums.length;
    let matchCount = 0;
    while (p1 < len) {
        let n1 = nums[p1];
        p2 = p1 + 1;
        while (p2 < len) {
            let n2 = nums[p2];
            p2++;
            if (n1 == n2) {
                result = true;
            }
        }
        p1++;
    }
    return result;
};

console.log(containsDuplicate([9, 9, 1]));
console.log(containsDuplicate([1, 2, 3]));

Solution 2:

/**
 * @param {number[]} nums
 * @return {boolean}
 */
var containsDuplicate2 = function(nums) {
    let obj = {};
    for (let num of nums) {
        if (obj[num]) return true;
        obj[num] = true;
    }
    return false;
};
console.log(containsDuplicate2([9, 9, 1]));
console.log(containsDuplicate2([1, 2, 3]));

Explanation:

1. This solution uses a object to store all of the numbers as keys.
2. Then it checks to see if a key already exists, if it does then we now know that we have a duplicated value in the array.