70. Leetcode solution in Java

class Solution {

    int [] cache = new int[46];

    public int climbStairs(int n) {

        if(n < 0) return 0;

        if(n == 0) return 1;

        int val = cache[n];

        if(val != 0)
            return val;

        val = climbStairs(n - 1) + climbStairs(n - 2);

        cache[n] = val;

        return val;
    }
}