array showing unknown behaviour

Question

3.00/5 (1 vote)

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#include<iostream>
#include<algorithm>

using namespace std;

int main()
{
    int arr[10];
    arr[0] = 1;
    arr[1] = 2;
    // sorting array
    sort(arr,arr+10);

    // printing array
    for(int i=0;i<10;i++)
    {
        cout<<arr[i]<<endl;
    }
    return 0;
}

the output is like this:
-1212121212121
-1212121212121
-1212121212121
-1212121212121
-1212121212121
-1212121212121
-1212121212121
1
2

what i want:

1
2

how can i do this

Posted 18-May-15 19:04pm

bhawin parkeria

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User 59241 · Accepted Answer · 2015-05-18T19:25:00

Sorting the array will NEVER return 1,2. It has 10 members. What values do the other members hold? Use your debugger to find out.

The array only has only two members initiallised and you sort the whole array. The other values of the array are unknown. They need to be set to something.

C#

int arr[10] = {0,0,0,0,0,0,0,0,0,0};

arr[0] = 1;
arr[1] = 2;

You may choose to sort only the first 2 (or initialised members) - you must then only display that subsection of the array not the whole 10 members. That will then give 1,2.

[Edit]
1. Yes you must set all values to known values - you can use a for loop or memset().

2. You can as I said sort a subset of your array - you must then only display those sorted values not the whole array.

CPallini · Accepted Answer · 2015-05-18T21:44:00

To set all items to a default known value, just change from

Quote:
int arr[10];

to

C++

int arr[10] = {0}; // init ALL the array items with value 0

Note the C++11 standard provides uniform initializers, the array container and ranged for loop:

C++

#include<iostream>
#include <array>
#include<algorithm>

using namespace std;

int main()
{
    array <int,10> arr{0}; // this initializes all the items with 0
    arr[0] = 1;
    arr[1] = 2;
    // sorting array
    sort(arr.begin(),arr.end());

    for ( auto  x : arr)
    {
      cout << x << endl;
    }
}

array showing unknown behaviour

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