268. Missing Number

Missing Number - LeetCodeLeetCode

with xor

/**
 * @param {number[]} nums
 * @return {number}
 */
var missingNumber = function(nums) {
    
    let ans = nums.length;
    for (let i = 0; i < nums.length; i++) {
        ans = ans^i^nums[i];
    }

    return ans;
};

time: O(N)

space: O(1)

/**
 * @param {number[]} nums
 * @return {number}
 */
var missingNumber = function(nums) {
    let sum = 0;
    let total = 0;
    
    for (let i = 0; i < nums.length; i++) {
        total += i + 1;
        sum += nums[i];
    }

    return total - sum;
};