題目

Given a non-empty array of integers, every element appears twice except for one. Find that single one.

Note:

Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory?

題意

找出陣列中，唯一一個沒有重複的值。
考慮到空間複雜度，無須額外的陣列是否能解決？

Example 1:

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

Example 2:

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

解題想法

先排序陣列，
唯一值的條件是，不論前後都不會有相同的值。

Solution

var singleNumber = function(nums) {
   nums.sort(function(a, b) {
        return a - b
    })
    
    for (let i = 0; i < nums.length; i += 2) {
        if (nums[i] !== nums[i+1] && nums[i] !== nums[i-1]) {
            return nums[i]
        }
    }
};