Error in reading input to an array in c++

Question

I was writing sorting algorithm when I encountered the following error.

Code:

int main()
{
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */
    int n;
    int a[100];
    cin >> n;
    for (int i = 1; i < n; ++i) {
        cin >> a[i];
    }
    //or use getlinee as getline (cin, fullName);
    int swap_count = 0;
    for (int i = 0; i < n - 1; ++i) {
        if (a[i] > a[i + 1]) {
            swap_count = swap_count + 1;
        }
    }

    if (swap_count != 0) {
        for (int p = n; p > 1; --p) {
            for (int q = 0; q < p - 1; ++q) {
                if (a[q] > a[q + 1]) {
                    int temp_var = a[q];
                    a[q] = a[q + 1];
                    a[q + 1] = temp_var;
                }
            }
        }
    }
    for (int i = 0; i < n; ++i) {
        cout << a[i] << " ";
    }
    return 0;
}

Input:

3
1 5 2

Output:

1 5 1878000832

On repeating with multiple values I found the last value of the series is being read wrong.

What is the reason for this problem and how do I resolve it?

Note: I know there are many alternative ways to input but I wanted to know why this one isn't working.

Check the indexing in your first loop again.

molbdnilo
– molbdnilo

2021-05-18 13:44:33 +00:00
Commented May 18, 2021 at 13:44 — molbdnilo
– molbdnilo, Commented May 18, 2021 at 13:44

MikeCAT · Accepted Answer · 2021-05-18 13:45:37Z

1

You are reading elements only from a[1], but your sorting begins from a[0].

Change

for (int i = 1; i < n; ++i)
{
    cin >> a[i];
}

to

for (int i = 0; i < n; ++i)
{
    cin >> a[i];
}

to read data also to a[0].

answered May 18, 2021 at 13:45

MikeCAT

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