public class Test_plus {
    public static int findNotDouble(int[] a) {
        int n=a.length;
        int result=a[0];
        int i;
        for(i=1;i<n;++i)
            result ^= a[i];
        return result;
    }
    public static void main(String[] args) {
        int array[]= {1,2,3,2,4,3,5,4,1};
        int num = findNotDouble(array);
        System.out.println(num);
    }

}
 

找出數組中只出現1次的數