C++ 阵列中的 C6385 和 C6201 警告

Question

i get a warning messages while doing merge between two sorted arrays into one sorted array as follows: and the error or warning messages that come to me are: C6385 & C6201

#include <iostream>
using namespace std;

int main()
{
    int arr1[5] = { 1,3,5,7,9 }, arr2[5] = { 0,2,4,6,8 }, arr3[10];

    for (int i = 1; i <= 9; i++)
        if (arr1[i] < arr2[i])
            arr3[i] = arr1[i];
        else
            arr3[i] = arr2[i];
        cout << arr3[10] << endl;

    return 0;
}

Answer 1

Array indices in C++ start from 0.

Also this statement

cout << arr3[10] << endl;

does not output the array. It tries to output a non-existent element with index 10 of the array.

And the loop is invalid because it tries to access memory beyond the arrays arr1 and arr2.

Your program can look the following way.

#include <iostream>
using namespace std;

int main()
{
    const size_t N = 5;
    int arr1[N] = { 1,3,5,7,9 }, arr2[N] = { 0,2,4,6,8 }, arr3[2 * N];

    for ( size_t i = 0, j = 0, k = 0; i < 2 * N; i++)
    {
        if ( arr2[k] < arr1[j])
            arr3[i] = arr2[k++];
        else
            arr3[i] = arr1[j++];
    }

    for ( const auto &item : arr3 ) cout << item << ' ';
    cout << '\n';

    return 0;
}

The same task can be performed with using the standard algorithm std::merge declared in the header <algorithm> .

For example

#include <iostream>
#include <iterator>
#include <algorithm>

int main()
{
    int a1[] = { 1, 3, 5, 7, 9 };
    int a2[] = { 0, 2, 4, 6, 8 };
    int a3[sizeof( a1 ) / sizeof( *a1 ) + sizeof( a2 ) / sizeof( *a2 )];

    std::merge( std::begin( a1 ), std::end( a1 ),
                std::begin( a2 ), std::end( a2 ),
                std::begin( a3 ) );

    for ( const auto &item : a3 ) std::cout << item << ' ';
    std::cout << '\n';

    return 0;
}

The program output is the same as shown above.

0 1 2 3 4 5 6 7 8 9