public void Peek_Test()
{
IStack <char> stack = new StackViaLinkedList <char>();
stack.Push('A');
stack.Push('B');
stack.Push('C');
stack.Push('D');
stack.Push('E');
stack.IsEmpty.Should().BeFalse();
stack.Count.Should().Be(5);
stack.Peek().Should().Be('E');
stack.Peek().Should().Be('E');
stack.Peek().Should().Be('E');
}
static void Main(string[] args)
{
StackViaLinkedList <int> viaLinkedList = new StackViaLinkedList <int>();
int i = 7;
viaLinkedList.Push(i);
viaLinkedList.Push(i * 2);
viaLinkedList.Push(i * 3);
Console.WriteLine(viaLinkedList.Peek());
Console.WriteLine(viaLinkedList.Pop());
}
/// <summary>
/// Algo1: 1. Keep a stack and every time a char(other than < or >) is encountered, make stack.top.child = newelement
/// Push this new element into the stack.
/// 2. When a < is encountered, do nothing
/// 3. When a > is encountered, do a pop()
/// </summary>
/// <param name="expression"></param>
/// <returns></returns>
private static TreeNode <char> CreateTreeFromExpression(char[] expression)
{
StackViaLinkedList <TreeNode <char> > stackForTree = new StackViaLinkedList <TreeNode <char> >();
TreeNode <char> headOfTree = null;
for (int expIndex = 0; expIndex < expression.Length; expIndex++)
{
if (expression[expIndex] == '<' || expression[expIndex] == ' ')
{
// No-op
}
else if (expression[expIndex] == '>')
{
SingleLinkedListNode <TreeNode <char> > top = stackForTree.Pop();
if (top == null)
{
throw new Exception("The expression is not well formed");
}
}
else
{
SingleLinkedListNode <TreeNode <char> > top = stackForTree.Peek();
TreeNode <char> currentNode = new TreeNode <char>(expression[expIndex]);
if (top == null)
{
headOfTree = currentNode;
}
else
{
top.Data.Children.Add(currentNode);
}
stackForTree.Push(currentNode);
}
}
// After this step the stack should be empty for a well formed expression
if (stackForTree.Top != null)
{
throw new Exception("The expression is not well formed");
}
return(headOfTree);
}