Euler's triangle sum (dynamic)

#include <iostream>

using namespace std;

unsigned get_number_of_levels(int number) {

    unsigned levels = 1;

    while (number > 0) {
        number -= levels++;
    }

    return levels - 1;
}

int main() {

    unsigned triangle_array[] = {75, 95, 64, 17, 47, 82, 18, 35, 87, 10, 20, 4, 82, 47, 65, 19, 1, 23, 75, 3, 34, 88, 2, 77, 73, 7, 63, 67, 99, 65, 4, 28, 6, 16, 70, 92, 41, 41, 26, 56, 83, 40, 80, 70, 33, 41, 48, 72, 33, 47, 32, 37, 16, 94, 29, 53, 71, 44, 65, 25, 43, 91, 52, 97, 51, 14, 70, 11, 33, 28, 77, 73, 17, 78, 39, 68, 17, 57, 91, 71, 52, 38, 17, 14, 91, 43, 58, 50, 27, 29, 48, 63, 66, 4, 68, 89, 53, 67, 30, 73, 16, 69, 87, 40, 31, 4, 62, 98, 27, 23, 9, 70, 98, 73, 93, 38, 53, 60, 4, 23};
    // unsigned triangle_array[] = {3, 7, 4, 2, 4, 6, 8, 5, 9, 3};

    unsigned levels = get_number_of_levels(sizeof(triangle_array)/sizeof(*triangle_array));
    int a, b;

    for (int i = levels; i > 0; --i) {
        a = i * (i-1) / 2;
        for (int j = 0; j < i - 1; ++j) {
            b = (i-1)*(i-2)/2;
            if (triangle_array[a + j] > triangle_array[a + j + 1]) {
                triangle_array[b + j] += triangle_array[a + j];
            }
            else {
                triangle_array[b + j] += triangle_array[a + j + 1];
            }
        }
    }

    cout << triangle_array[0] << endl;

    return 0;
}