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In QueueIterator
Item item = q[i % q.length];
Why not q[(first + i) % q.length];?

Hello:
In the Ex_1_1_16 Java code, I don't understand why the result is 311361142246??The question is to examine what?
Can you explain it for me ? :)

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In the Ex_1_1_27a.java binomial() function, I test the code,but there is a error :

Exception in thread "main" java.lang.Error: Unresolved compilation problem:
The method incremen() is undefined for the type Counter

In your program, the incremen() is undefined, so, how can the this program run successfully?

I know the Counter c is used to cumulative the number of recursive calls, but can't understand why use the function c.incremen().

I think now that c is used to cumulative the number of recursive calls, I use this program:

public static double binomial( int n, int k, double p, int c) {
        if ( n == 0 && k == 0) {
            return 1.0;
        }
        if ( n < 0 || k < 0) {
            return 0.0;
        }

        c++;  

        return (1.0 - p) * binomial( n - 1, k, p, c) + p * binomial( n - 1, k - 1, p, c);
    }
    public static void main(String[] args) {
        int n = Integer.parseInt(args[0]),
            k = Integer.parseInt(args[1]);
        double p = Double.parseDouble(args[2]);

        int c = 0;

        double b = binomial(n, k, p, c);

        StdOut.println(b);
        StdOut.println(c);
    }

I test 10 5 0.5, but I get the result: 0.24609375 0.

I hope to help me Solve this doubt,thanks a lot !

I think s[a[i]][i]++; is right not s[i][a[i]]++; in 22 line num. Am I wrong?

Thanks for your work on this. I'm currently going over the book and I have been a little off by the section on Heapsort. One of the things that I was confused about was dealing with the index 1 to N in the sorting method. I noticed from your implementation that you use -1 in the swap and in the less but have you tested?

class Heap
  # Trickledown
  def sink(a, k, n)
    while 2 * k <= n
      j = 2 * k # child

      if !a[j + 1].nil? # check if there is a right child
        j += 1 if j > 1 && less(a, j, j + 1) # if left child less than right child
      end

      break if !less(a, k, j) # If parent greater than child break

      swap(a, k, j)
      k = j
    end
  end

  def sort(a)
    n = a.length
    k = n / 2

    while k >= 1
      sink(a, k, n)
      k -= 1
    end

    while n > 1
      swap(a, 1, n)
      n -= 1
      sink(a, 1, n)
    end
    a
  end

  def less(pq, i, j)
    pq[i - 1] < pq[j - 1]
  end

  def swap(a, i, j)
    temp = a[i - 1]
    a[i - 1] = a[j - 1]
    a[j - 1] = temp
  end
end

When I do your implementation in Ruby I get the error for as the answer ["A", "M", "E", "L", "E", "O", "P", "R", "S", "T", "X"] and I haven't been able to figure out why.

I created the following post on Stackoverflow
https://stackoverflow.com/questions/63634906/ruby-heapsort-sink-undefined-method-for-nilnilclass

trying to figure out where am I off.