题解 | #缺失数字#（异或）
缺失数字
http://www.nowcoder.com/practice/9ce534c8132b4e189fd3130519420cde
异或 时间复杂度O(n)
class Solution {
public:
int solve(vector<int>& a) {
int n = a.size();
if(n == 0) return 0;
int result = 0;
for(int i = 0; i < n; i++){
result ^= a[i];
result ^= i+1;
}
return result;
}
};
