optimized code

4.3.2.cpp

#include <vector>
#include <iostream>
using namespace std;

class Matrix{
public:
	Matrix(int n) {
		matrix.resize(n*(n+1)/2, 0);
		size = n;
	}
	void do_it() {
		for(int y = 1; y <= size; ++y)
			for(int x = 1; x <= size-y+1; ++x)
				matrix[(2*size - (y-1))*(y-1)/2 + (x-1)] = calc_vop(x, y);
	}
	long long get_vop(int x, int y){
		return calc_vop(x,y);
	}
private:
	long long calc_vop(int x, int y) {
		long long sum = 0;
		for (int i = 1; i <= y; ++i) {
			if (x-i < 0)
				break;
			if (x-i == 0)
				sum += 1;
			else if(i-1 != 0){
				sum += matrix[(i-2)*size - float((i-2)*(i-2))/2 + (x-i-1)];
			}
	}
	return sum;
}
	vector<long long> matrix;
	int size;
};

long long get_number(int n) {
	if (n < 0)
		return 0;
	if (n == 0)
		return 1;

	Matrix matrix(n);
	matrix.do_it();
	long long res =matrix.get_vop(n, n);

	return res;
}

int main() {
	int n;
	cin >> n;
	cout << get_number(n);
	return 0;
}