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[C++]LeetCode: 66 Single Number

2015-01-05

题目: 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 y

题目:

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?

思路:

要求线性时间完成,并且不使用额外的存储空间。

**非常之巧妙**

使用异或来排除double值,剩下的就是single one. 异或具有可交换性,顺序可变。

比如给出数组{2,1,4,5,2,4,1} ,求异或,2^1^4^5^2^4^1 <=> (2^2)^(1^1)^(4^4)^(5) <=> (0)^(0)^(0)^5 = 5

AC Code:

class Solution {
public:
    int singleNumber(int A[], int n) {
        int ret;
        ret = A[0];
        
        for(int i = 1; i < n; i++)
        {
            ret ^= A[i];
        }
        
        return ret;
    }
};


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