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Single Number

题目

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

You must implement a solution with a linear runtime complexity and use only constant extra space.

Example 1:

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

Example 2:

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

Example 3:

Input: nums = [1]
Output: 1

Constraints:

  • 1 <= nums.length <= 3 * 104
  • -3 * 104 <= nums[i] <= 3 * 104
  • Each element in the array appears twice except for one element which appears only once.

思路

最简单思路当然是用HashMap来处理。但是HashMap的话,空间复杂度就是O(n),而不是O(1)。

该题需要利用数字A异或它本身等于0。不刷题根本想不到。。

代码

class Solution {
    public int singleNumber(int[] nums) {
        int result = 0;
        for (int num: nums) {
            result ^= num;
        }   
        return result;
    }
}
Published in数据结构和算法

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