Number of decimal numbers of length k, that are strict monotone

// CPP program to count numbers of k
// digits that are strictly monotone.
#include <cstring>
#include <iostream>

int static const DP_s = 9;

int getNumStrictMonotone(int len)
{
	// DP[i][j] is going to store monotone
	// numbers of length i+1 considering
	// j+1 digits (1, 2, 3, ..9)
	int DP[len][DP_s];
	memset(DP, 0, sizeof(DP));

	// Unit length numbers
	for (int i = 0; i < DP_s; ++i)
		DP[0][i] = i + 1;

	// Building dp[] in bottom up
	for (int i = 1; i < len; ++i)
		for (int j = 1; j < DP_s; ++j)
			DP[i][j] = DP[i - 1][j - 1] + DP[i][j - 1];	
	
	return DP[len - 1][DP_s - 1];
}

// Driver code
int main()
{
	std::cout << getNumStrictMonotone(2);
	return 0;
}