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0222-CountCompleteTreeNodes.cs
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//-----------------------------------------------------------------------------
// Runtime: 112ms
// Memory Usage: 32.9 MB
// Link: https://leetcode.com/submissions/detail/357621851/
//-----------------------------------------------------------------------------
using System;
namespace LeetCode
{
public class _0222_CountCompleteTreeNodes
{
public int CountNodes(TreeNode root)
{
if (root == null) { return 0; }
// Find Depth
var current = root;
var depth = 0;
while (current.left != null)
{
current = current.left;
depth++;
}
if (depth == 0) return 1;
var count = (int)Math.Pow(2, depth) - 1;
var l = 0;
var r = count;
while (l <= r)
{
var mid = l + (r - l) / 2;
if (FindNode(root, mid, count, depth))
l = mid + 1;
else
r = mid - 1;
}
return count + l;
}
public bool FindNode(TreeNode root, int index, int count, int depth)
{
var l = 0;
var r = count;
for (int i = 0; i < depth; i++)
{
var mid = l + (r - l) / 2;
if (index <= mid)
{
root = root.left;
r = mid;
}
else
{
root = root.right;
l = mid + 1;
}
}
return root != null;
}
}
}