How can a recursive Java method be memoized?

Question

So I\'ve built this program to build different stair cases. Essentially the problem is: Given an integer N, how many different ways can you build the staircase. N is guarant

Answer 1

Use a small class to hold the pairs (height, bricks), say:

private static class Stairs {
    private int height;
    private int bricks;
    Stairs(int height, int bricks) {
        this.height = height; this.bricks = bricks;
    }
}

Then use a global HashMap, initialized in the main():

map = new HashMap();

In the bricks() function, check if the solution for a particular (height, bricks) pair is in the map. If yes, just return it from the map via a call to the get() method. Otherwise, do the computation:

Stairs stairsObj = new Stairs(height, bricks);
if(map.get(stairsObj) == null) {
    // Put your compute code here
}

Before every return statement in the function, add two additional statements. Something like:

int result = ;
map.put(stairsObj, result);
return result;