A - Insert

https://atcoder.jp/contests/abc361/tasks/abc361_a

https://atcoder.jp/contests/abc361/submissions/55260626

int n, k, x;
vector<int> a;

int main()
{
    cin >> n >> k >> x;

    a.resize(n+1);

    for(int i=0; i<n+1; i++){
        if (i == k){
            a[i] = x;
        } else {
            cin >> a[i];
        }
    }

    for(int i=0; i<n+1; i++){
        cout << a[i] << " ";
    }

    return 0;
}

B - Intersection of Cuboids

https://atcoder.jp/contests/abc361/tasks/abc361_b

https://atcoder.jp/contests/abc361/submissions/55334640

int a, b, c, d, e, f;
int g, h, i, j, k, l;

bool check_if_intersected(array<int, 2>& one_segment, array<int, 2>& two_segment){
    int one_start = one_segment[0];
    int one_stop = one_segment[1];
    
    int two_start = two_segment[0];
    int two_stop = two_segment[1];

    /*
    intersection:
    one        ---------------
    two         -------------
    */
    if (two_start >= one_start){
        if (one_stop > two_start){
            return true;
        }
    }

    /*
    intersection:
    one            ---------------
    two     -------------
    */
    if (one_start >= two_start){
        if (two_stop > one_start){
            return true;
        }
    }
    
    return false;
}

int main()
{
    cin >> a >> b >> c >> d >> e >> f;
    cin >> g >> h >> i >> j >> k >> l;

    array<array<int,2>, 3> dimensions_of_one{{
        {a, d}, // x
        {b, e}, // y
        {c, f}  // z
    }};

    array<array<int,2>, 3> dimensions_of_two{{
        {g, j}, // x
        {h, k}, // y
        {i, l}  // z
    }};

    for(int i=0; i<3; i++){
        array<int, 2>& one_segment = dimensions_of_one[i];
        array<int, 2>& two_segment = dimensions_of_two[i];
        /*
        check if two segment has intersection.
        */
        if (!check_if_intersected(one_segment, two_segment)){
            cout << "No" << endl;
            return 0;
        }
    }

    cout << "Yes" << endl;

    return 0;
}