The figures appear only once Leetcode--

Given a non-empty array of integers, in addition to an element appears only once, the rest of each element appears twice. To find out that only appears once in the elements.

Description:

　　Your algorithm should have linear time complexity. You can not use the extra space to achieve it?

Example 1:

　　Input: [2,2,1]
　　Output: 1

Example 2:

　　Input: [4,1,2,1,2]
　　Output: 4

 

C ++ solution

/ * 
　　XOR Solution: XOR operation is commutative, a ^ b ^ a = a ^ a ^ b = b, ans therefore corresponds nums [0] ^ nums [1 ] ^ nums [2] ^ nums [3] ^ nums [4] ..... 
　　then according to the commutative equal to merge together XOR (zero), 
　　then only occurs once the XOR elements, so that the final result is, appeared only elements (0 ^ arbitrary value = value) time 
* / 

class Solution { 
public: 
    int singleNumber (Vector <int> & the nums) { 
        int ANS = the nums [0]; 
        for (int I =. 1; I < nums.size (); I ++) { 
            ANS = ^ ANS the nums [I]; 
        } 
        return ANS; 
    } 
};