Leetcode 645 - Set Mismatch

Note:

  • Sort first so we can find the duplicates.
  • While iterating, find sum and the duplicates.
  • The sum was supposed to be (1 + n) * n / 2.
  • The diff between correctSum and sum is how much we should add to the duplicates.
  • And that’s the missing num.

Question:

You have a set of integers s, which originally contains all the numbers from 1 to n. Unfortunately, due to some error, one of the numbers in s got duplicated to another number in the set, which results in repetition of one number and loss of another number.

You are given an integer array nums representing the data status of this set after the error.

Find the number that occurs twice and the number that is missing and return them in the form of an array.

Example:

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

Code:

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/**
* @param {number[]} nums
* @return {number[]}
*/
var findErrorNums = function (nums) {
nums.sort((a, b) => a - b);
const n = nums.length;
let ans = [0, 0];
let sum = 0;
for (let i = 0; i < nums.length; i++) {
if (nums[i] === nums[i + 1]) ans[0] = nums[i];
sum += nums[i];
}
ans[1] = ((1 + n) * n / 2) + ans[0] - sum;
return ans;
};