翻譯

給定一個整型陣列，除了某個元素外其餘元素均出現兩次。找出這個只出現一次的元素。

備註：
你的演算法應該是一個線性時間複雜度。你可以不用額外空間來實現它嗎？

原文

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?
 

分析

程式碼

class Solution {
public:
 unsigned int FindFirstBigIs1(int num) {
    int indexBit = 0;
    while (((num & 1) == 0) && (indexBit < 8 * sizeof(int))) {
        num = num >> 1;
        ++indexBit;
    }
    return indexBit;
}

int singleNumber(vector<int>& nums) {
    if
 
 (nums.size() <= 0) return NULL;

    int resultExclusiveOR = 0;
    for (int i = 0; i < nums.size(); ++i)
        resultExclusiveOR ^= nums[i];

    unsigned int indexOf1 = FindFirstBigIs1(resultExclusiveOR);

    int singleNum = 0;
    for (int j = 0; j < nums.size(); ++j) {
            singleNum ^= nums[j];
    }
    return
 
 singleNum;
}
};