LeetCode 136. Single Number 解题报告

136. Single Number

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Question

Total Accepted: 113794  Total Submissions: 234460  Difficulty: Medium

Given an 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?

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  Hash Table Bit Manipulation

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  (M) Single Number II (M) Single Number III (M) Missing Number (H) Find the Duplicate Number

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    题目要求线性时间复杂度，并且不需要额外的存储空间。这里利用异或运算性质求解

1、交换律

2、结合律（即(a^b)^c == a^(b^c)）

3、对于任何数x，都有x^x=0，x^0=x

4、自反性 A XOR B XOR B = A xor  0 = A

    AC代码如下：

public class SingleNumber {

	public int singleNumber(int[] nums) {
		int a = nums[0];
		for (int i = 1; i < nums.length; i++) {
			a ^= nums[i];
		}
		return a;
	}
}