public int PathSum(TreeNode root, int sum)
{
var sumCount = 0;
CalcSum(root, sum, 0, ref sumCount);
return(sumCount);
}
private TreeNode BuildTree(int?[] input)
{
var root = new TreeNode(input[0].Value);
AddLeaves(root, input, 1, 0);
return(root);
}
private void AddLeaves(TreeNode current, int?[] input, int level, int num)
{
var inputIndex = (int)Math.Pow(2, level) - 1 + num;
if (input.Length < inputIndex + 1)
{
return;
}
if (input[inputIndex] != null)
{
current.left = new TreeNode(input[inputIndex].Value);
AddLeaves(current.left, input, level + 1, num);
}
if (input[inputIndex + 1] != null)
{
current.right = new TreeNode(input[inputIndex + 1].Value);
AddLeaves(current.right, input, level + 1, num + 2);
}
}
private void CalcSum(TreeNode current, int targetSum, int currSum, ref int sumCount)
{
if (current == null)
{
return;
}
currSum += current.val;
if (currSum == targetSum)
{
sumCount++;
return;
}
else
{
CalcSum(current.left, targetSum, currSum, ref sumCount);
CalcSum(current.right, targetSum, currSum, ref sumCount);
}
CalcSum(current.left, targetSum, 0, ref sumCount);
CalcSum(current.right, targetSum, 0, ref sumCount);
}
public TreeNode(int val = 0, TreeNode left = null, TreeNode right = null)
{
this.val = val;
this.left = left;
this.right = right;
}
