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0315-CountOfSmallerNumbersAfterSelf.cs
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//-----------------------------------------------------------------------------
// Runtime: 256ms
// Memory Usage:
// Link:
//-----------------------------------------------------------------------------
using System.Collections.Generic;
namespace LeetCode
{
public class _0315_CountOfSmallerNumbersAfterSelf
{
public IList<int> CountSmaller(int[] nums)
{
if (nums.Length == 0) return nums;
int[] counts = new int[nums.Length];
Node root = new Node(nums[nums.Length - 1]);
for (int i = nums.Length - 2; i >= 0; i--)
counts[i] = Insert(root, nums[i]);
return counts;
}
private int Insert(Node root, int value)
{
if (value < root.Value)
{
root.LessCount++;
if (root.Left == null)
{
root.Left = new Node(value);
return 0;
}
return Insert(root.Left, value);
}
else if (root.Value < value)
{
if (root.Right == null)
{
root.Right = new Node(value);
return root.EqualCount + root.LessCount;
}
return root.EqualCount + root.LessCount + Insert(root.Right, value);
}
else
{
root.EqualCount++;
return root.LessCount;
}
}
public class Node
{
public int Value;
public int EqualCount = 1;
public int LessCount = 0;
public Node Left;
public Node Right;
public Node(int value)
{
this.Value = value;
}
}
}
}