LeetCode 30 days Challenge - Day 1
本系列将对LeetCode新推出的30天算法挑战进行总结记录，旨在记录学习成果、方便未来查阅，同时望为广大网友提供帮助。
Single Number
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?
Example 1:
Input: [2,2,1]
Output: 1
Example 2:
Input: [4,1,2,1,2]
Output: 4
Solution
题目要求分析：给定非空数组，找到单独出现的元素。
-
时间复杂度：O(n)
-
空间复杂度：O(1)
解法：
关键利用异或运算符^，对于异或运算：
- a ^ a == 0
- a ^ 0 == a
- a ^ b ^ c = a ^ c ^ b
结合题目给出除了目标元素外，其余元素各出现两次，不难想到遍历整个数组，逐个将元素进行异或运算，最后剩下的元素即为目标。
int singleNumber(vector<int>& nums) {
int res = 0;
for (int n : nums) res ^= n;
return res;
}
传送门：Single Number
2020/4 Karl
