#268 - Missing Number

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Problem Description

Given an array `nums` containing `n` distinct numbers in the range `[0, n]`, return the only number in the range that is missing from the array.

Follow up: Could you implement a solution using only `O(1)` extra space complexity and `O(n)` runtime complexity?

Solution

/**
 * @param {number[]} nums
 * @return {number}
 */
var missingNumber = function(nums) {
  let result = 0;

  for (let i = 0; i < nums.length; i++) {
    result += i + 1 - nums[i];
  }

  return result;
};