136. Single Number(技巧性非常强)

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用到6

class Solution {
public:
    int singleNumber(vector<int>& nums) {
        if(nums.empty()) return -1;
        int result = 0;
        for(auto iter = nums.begin(); iter != nums.end(); iter++){
            result = result ^ *iter;
        }
        return result;
    }
};