public static void Test()
{
/// +
/// / \
/// * -
/// / \ / \
/// 5 4 100 20
/// result: 5*4 + (100-20) = 100
BinaryNodeExpression root = new BinaryNodeExpression("+");
root.Left = new BinaryNodeExpression("*");
root.Left.Left = new BinaryNodeExpression("5");
root.Left.Right = new BinaryNodeExpression("4");
root.Right = new BinaryNodeExpression("-");
root.Right.Left = new BinaryNodeExpression("100");
root.Right.Right = new BinaryNodeExpression("20");
Console.Write("Tree 1 result: " + EvaluateTree(root));
BinaryNodeExpression root2 = new BinaryNodeExpression("+");
root2.Left = new BinaryNodeExpression("*");
root2.Left.Left = new BinaryNodeExpression("5");
root2.Left.Right = new BinaryNodeExpression("4");
root2.Right = new BinaryNodeExpression("-");
root2.Right.Left = new BinaryNodeExpression("100");
root2.Right.Right = new BinaryNodeExpression("/");
root2.Right.Right.Left = new BinaryNodeExpression("20");
root2.Right.Right.Right = new BinaryNodeExpression("2");
Console.Write("\nTree 2 result: " + EvaluateTree(root2));
}
/// <summary>
/// -
/// / \
/// + *
/// / \ / \
/// a b * g
/// / \
/// e f
/// infix expression is
/// a + b - e* f * g
/// </summary>
public static void PrintExpression()
{
String postfix = "ab+ef*g*-";
BinaryNodeExpression root = ConstructTree(postfix);
Console.WriteLine("infix expression is");
PrintExpressionTreeInOrder(root);
}
// Utility function to do inorder traversal
private static void PrintExpressionTreeInOrder(BinaryNodeExpression t)
{
if (t != null)
{
PrintExpressionTreeInOrder(t.Left);
Console.Write(t.Value + " ");
PrintExpressionTreeInOrder(t.Right);
}
}
// Returns root of constructed tree for given
// postfix expression
/// <summary>
/// Construction of Expression Tree:
/// Now For constructing expression tree we use a stack.We loop through input expression and do following for every character.
/// 1) If character is operand push that into stack
/// 2) If character is operator pop two values from stack make them its child and push current node again.
/// At the end only element of stack will be root of expression tree.
/// </summary>
/// <param name="postfix"></param>
/// <returns></returns>
public static BinaryNodeExpression ConstructTree(string postfix)
{
Stack <BinaryNodeExpression> st = new Stack <BinaryNodeExpression>();
BinaryNodeExpression t, t1, t2;
// Traverse through every character of
// input expression
var postFixCharArray = postfix.ToCharArray();
for (int i = 0; i < postFixCharArray.Length; i++)
{
// If operand, simply push into stack
if (!IsOperator(postFixCharArray[i].ToString()))
{
t = new BinaryNodeExpression(postFixCharArray[i].ToString());
st.Push(t);
}
else // operator
{
t = new BinaryNodeExpression(postFixCharArray[i].ToString());
// Pop two top nodes
// Store top
t1 = st.Pop(); // Remove top
t2 = st.Pop();
// make them children
t.Right = t1;
t.Left = t2;
st.Push(t);
}
}
// only element will be root of expression
// tree
t = st.Peek();
st.Pop();
return(t);
}
private static int EvaluateTree(BinaryNodeExpression root)
{
// empty tree
if (root == null)
{
return(0);
}
// leaf node i.e, an integer
if (root.Left == null && root.Right == null)
{
return(Convert.ToInt32(root.Value));
}
// Evaluate left subtree
int l_val = EvaluateTree(root.Left);
// Evaluate right subtree
int r_val = EvaluateTree(root.Right);
// Check which operator to apply
if (root.Value == "+")
{
return(l_val + r_val);
}
if (root.Value == "-")
{
return(l_val - r_val);
}
if (root.Value == "*")
{
return(l_val * r_val);
}
return(l_val / r_val);
}
public static List <List <int> > verticalOrder(BinaryNodeExpression root)
{
List <List <int> > result = new List <List <int> >();
Dictionary <int, List <int> > dic = new Dictionary <int, List <int> >();
int minHorizontalDistnace = int.MaxValue;
int maxHorizontalDistnace = int.MinValue;
Queue <NodeWithHorizontalDistance> q = new Queue <NodeWithHorizontalDistance>();
q.Enqueue(new NodeWithHorizontalDistance(root, 0));
while (q.Count > 0)
{
NodeWithHorizontalDistance cur = q.Dequeue();
dic.Add(cur.horizontalDistnace, new List <int> {
Convert.ToInt32(cur.root.Value)
});
minHorizontalDistnace = Math.Min(minHorizontalDistnace, cur.horizontalDistnace);
maxHorizontalDistnace = Math.Max(maxHorizontalDistnace, cur.horizontalDistnace);
if (cur.root.Left != null)
{
q.Enqueue(new NodeWithHorizontalDistance(cur.root.Left, cur.horizontalDistnace - 1));
}
if (cur.root.Right != null)
{
q.Enqueue(new NodeWithHorizontalDistance(cur.root.Right, cur.horizontalDistnace + 1));
}
}
for (int i = minHorizontalDistnace; i <= maxHorizontalDistnace; i++)
{
result.Add(dic.GetValueOrDefault(i));
}
return(result);
}
public NodeWithHorizontalDistance(BinaryNodeExpression root, int horizontalDistnace)
{
this.root = root;
this.horizontalDistnace = horizontalDistnace;
}
public BinaryNodeExpression(string value)
{
this.Value = value;
this.Left = this.Right = null;
}