Fibonacci Bottom Up & Top Down

// bottom up (tabulation)

static int fibBottomUp(int n){
  int[] fib = new int[n + 1];
  fib[0] = 1;
  fib[1] = 1;
  
  for(int i = 2; i <= n; i++){
    fib[i] = fib[i - 2] + fib[i - 1];
  }
  
  return fib[n];
}

// top down (memoization)

static int fibTopDown(int n){
  int[] fib = new int[n + 1];
  
  if(fib[n] == null){
    if(n <= 1){
      fib[n] = 1;
    }
    else{
      fib[n] = fibTopDown(n - 2) + fibTopDown(n-1);
    }
  }
  return fib[n];
}