начало дерева отрезок

#include <iostream>
#include <math>
#include <string>
using namespace std;

const MAX = 2e5;

class Segment_Tree
{
    int* tree;
    int tree_size;
    int count_numbers;
    std::vector<int> numbers;

public:
    segment_tree();
    segment_tree(int count_numbers);
};

void Segment_Tree::build_tree(const std::vector<int>& numbers, int v, int tl, int tr)
{

    if (tr - tl == 1)
        tree[v] = numbers[tl];
    else
    {
        int tm = (tl + tr) / 2;
        build (numbers, v*2+1, tl, tm);
        build (numbers, v*2+2, tm, tr);
        tree[v] = tree[v*2+1] + tree[v*2+2];
    }

}

int Segment_Tree::to_deg_of_two(std::vector<int>& numbers, int count_numbers)
{

    int p = 1;
    while (count_numbers > p)
        p *= 2;

    for (int i =0; i < p-count_numbers; ++i)
        numbers.push_back(MAX);

    return 2*p;

}

Segment_Tree::Initialize(int count_numbers)
{

    this->count_numbers = count_numbers;
    for (int i =1; i <= count_numbers; ++i)
        numbers.push_back(i);

    this->tree_size = to_deg_of_two(numbers, count_numbers);
    this->tree = new int[tree_size];
    build_tree(numbers, 0, 0, count_numbers);
}

Segment_Tree::get_min(int l, int r)
{

}


Segment_Tree::find_spot(char start_number)
{
    int start = stoi(start_number);
    int min_num = get_min(start, this->count_numbers-1);

    if (min_num == MAX)
    {
        min_num = get_min(0, start-1);

        if (min_num == MAX)
            return -1 :
        else
        {
            set(min_num-1,MAX);
            return min_num;
        }
    }

    else
    {
        set(min_num-1,MAX);
        return min_num;
    }

}

Segment_Tree::free_up(char number)
{
    int num = stoi(number);

    if tree[num-1] == MAX
    {
        set(num-1,num);
        return 0;
    }
    else
        return -2;
}

int main()
{

    int n,m;
    cin >> n >> m;

    Segment_Tree tree;
    tree.Initialize(n);

    string s[3];
    for (int i=0; i < m; ++i)
    {
        cin >> s;
        if (s[0] == "+")
            find_spot(s[3]);
        else
            free_up(s[3]);
    }

    return 0;
}