1 задача

#include < iostream>
#include <vector>

using namespace std;

vector<int> build(vector<int> array,const int& lenght)
{
    if (lenght % 2 == 0)
    {
        vector<int> output(lenght * 2 - 1);
        for (int i = 0; i < lenght; i++)
        {
            output[lenght - 1 + i] = array[i];
        }
        for (int i = lenght - 2; i >= 0; i--)
        {
            output[i] = output[i * 2 + 1] + output[i * 2 + 2];
        }
        return output;
    }
    else
    {
        vector<int> output((lenght+1) * 2 - 1);
        for (int i = 0; i < lenght; i++)
        {
            output[lenght + i] = array[i];
        }
        for (int i = lenght - 1; i >= 0; i--)
        {
            output[i] = output[i * 2 + 1] + output[i * 2 + 2];
        }
        return output;
    }
}

int sum(int l, int r, int x, int lx, int rx,const vector<int>& array)
{
    if (l >= rx or lx >= r)
        return 0;
    if (lx >= l and rx <= r)
        return array[x];
    int m = (lx + rx) / 2;
    int sl = sum(l, r, 2 * x + 1, lx, m, array);
    int sr = sum(l, r, 2 * x + 2, m, rx, array);
    return sl + sr;
}
int main()
{
    int x;
    int number;
    vector<int> array;
    cin >> number;
    for(int i =0;i<number; i++)
    {
        cin >> x;
        array.push_back(x);
    }
    cout << endl << endl;
    vector<int> a = build(array, array.size());

    int left;
    int right;
    int node;
    cin >> left >> right >> node;
    cout << sum(left,right,node,0,a.size(),a);
}