need help c++

[kiril.zh]

Hello everyone,

 

I began solving problems on HackerRank and I can't figure out the one with the lonely integer. The problem statement is: "There are N integers in an array A. All but one integer occur in pairs. Your task is to find out the number that occurs only once." Below is the code they provide and they ask from me to figure out what the lonelyinteger function should do. I have trouble completing the task because I've never worked with vectors before and I don't have a clue of how to implement the xor operator.

 

Any help would be greatly appreciated!

#include <map>#include <set>#include <list>#include <cmath>#include <ctime>#include <deque>#include <queue>#include <stack>#include <bitset>#include <cstdio>#include <limits>#include <vector>#include <cstdlib>#include <numeric>#include <sstream>#include <iostream>#include <algorithm>using namespace std;int lonelyinteger(vector < int > a) {return 0;}int main() {    int res;        int _a_size;    cin >> _a_size;    cin.ignore (std::numeric_limits<std::streamsize>::max(), '\n');     vector<int> _a;    int _a_item;    for(int _a_i=0; _a_i<_a_size; _a_i++) {        cin >> _a_item;        _a.push_back(_a_item);    }        res = lonelyinteger(_a);    cout << res;        return 0;}

[madknight3]

If performance isn't a large concern you can accomplish this with nested for loops.

[Midnight]

You don't need a vector.

 

Just XOR all of the input.

 

For example,

 

lonely ^= input;

 

where lonely is the lonely integer and input is the input in the test data.

[Guest]

The bitwise XOR operator is binary (takes two arguments):

int a = 0x0;int b = 0xf;int result = a ^ b;

You can also perform a compound assignment with XOR, as in the above post:

int a = 0x0;a ^= 0xff;