Ways to climb steps 3 steps at once.

public class ClimbingSteps3StepsOnce {
    public static void main(String[] args) {
        System.out.println(getWays(10));
    }

    private static int getWays(int steps) {
        if (steps == 0 || steps == 1) {
            return 1;
        }
        if (steps == 2) {
            return 2;
        }

        if (steps == 3) {
            return 4;
        }

        int[] ways = new int[steps + 1];
        ways[1] = 1;
        ways[2] = 2;
        ways[3] = 4;

        for (int i = 4; i < ways.length; i++) {
            ways[i] = ways[i - 1] + ways[i - 2] + ways[i - 3];
        }

        return ways[steps];
    }
}