#include <stdio.h>

#include <unistd.h>

#include <iostream>

#include <memory.h>

#include <string.h>

int main()

{

        typedef int data_type;

        data_type a[] = {1,4,6,7,7,8,4,9,1,7,6,4,1,2,0,0};

        const char* hint = "The original number is:\n ";

        write(STDOUT_FILENO, hint, strlen(hint));

        for(int i = 0; i < sizeof(a)/sizeof(a[0]); ++i)

        {

                printf("%d ", a[i]);

        }

        printf("\n");

        // get the max value

        int max = a[0];

        for(int i = 0;i < sizeof(a)/sizeof(data_type);++i)

        {

                if(a[i] > max)

                {

                        max = a[i];

                }

        }

        // allocate an space. you can use bitwise if the space is too big.

        data_type* p = new data_type[max + 1];

        memset(p, 0, max + 1);

        int cnt = 0;

        for(int i = 0;i < sizeof(a)/sizeof(data_type);++i)

        {

                if(*(p + a[i]) == -1)

                {

                        ++cnt;

                }

                else

                {

                        *(p + a[i]) = -1;

                }

        }

        std::cout << "The dumplicated number is " << cnt << std::endl;

        return 0;

}

[root@ba algr]# g++ array.cpp -g

[root@ba algr]# ./a.out

The original number is:

 1 4 6 7 7 8 4 9 1 7 6 4 1 2 0 0

The dumplicated number is 8

[root@ba algr]#