#645. Set Mismatch

https://leetcode.com/problems/set-mismatch/description/?envType=daily-question&envId=2024-01-22

/**
 * @param {number[]} nums
 * @return {number[]}
 */
var findErrorNums = function(nums) {
    const counter = new Array(nums.length + 1).fill(0)

    for (let num of nums) {
        counter[num]++
    }

    let missing = -1, duplicate = -1

    for (let i = 1; i < counter.length; i++) {
        if (counter[i] === 2) {
            duplicate = i
        } else if (counter[i] === 0) {
            missing = i
        }
    }

    return [duplicate, missing]

};