public static BinaryTreeNodeWithSize <int> FindKthNodeBinaryTree(BinaryTreeNodeWithSize <int> tree, int k)
{
var iter = tree;
while (iter != null)
{
var leftSize = iter.Left?.Size ?? 0;
if (leftSize + 1 < k) // k-th node must be in right subtree of iter.
{
k -= leftSize + 1;
iter = iter.Right;
}
else if (leftSize == k - 1) // k-th is iter itself.
{
return(iter);
}
else // k-th node must be in left subtree of iter.
{
iter = iter.Left;
}
}
// If k is between 1 and the tree size, this line is unreachable .
return(null);
}
public void FindKthNodeBinaryTree()
{
var A = new BinaryTreeNodeWithSize <int>()
{
Data = 314
};
var B = new BinaryTreeNodeWithSize <int>()
{
Data = 6
};
var C = new BinaryTreeNodeWithSize <int>()
{
Data = 271
};
var D = new BinaryTreeNodeWithSize <int>()
{
Data = 28
};
var E = new BinaryTreeNodeWithSize <int>()
{
Data = 0
};
var F = new BinaryTreeNodeWithSize <int>()
{
Data = 561
};
var G = new BinaryTreeNodeWithSize <int>()
{
Data = 3
};
var H = new BinaryTreeNodeWithSize <int>()
{
Data = 17
};
var I = new BinaryTreeNodeWithSize <int>()
{
Data = 6
};
var J = new BinaryTreeNodeWithSize <int>()
{
Data = 2
};
var K = new BinaryTreeNodeWithSize <int>()
{
Data = 1
};
var L = new BinaryTreeNodeWithSize <int>()
{
Data = 401
};
var M = new BinaryTreeNodeWithSize <int>()
{
Data = 641
};
var N = new BinaryTreeNodeWithSize <int>()
{
Data = 257
};
var O = new BinaryTreeNodeWithSize <int>()
{
Data = 271
};
var P = new BinaryTreeNodeWithSize <int>()
{
Data = 28
};
A.Left = B;
A.Right = I;
B.Left = C;
B.Right = F;
C.Left = D;
C.Right = E;
F.Right = G;
G.Left = H;
I.Left = J;
I.Right = O;
J.Right = K;
K.Left = L;
K.Right = N;
L.Right = M;
O.Right = P;
var result = Solution.FindKthNodeBinaryTree(A, 10);
result.Should().BeEquivalentTo(L);
}
