How to calculate the sum of the left leaves of a binary tree
Given a binary tree. Calculate the
sumof theleft leaves
Example
Output:7
/* Definition for TreeNode
public class TreeNode
{
public int Value;
public TreeNode Left;
public TreeNode Right;
public TreeNode(int value)
{
Value = value;
}
}
*/
public sealed class Solution
{
public int LeftLeavesSum(TreeNode root)
{
}
}
Approach
To solve this problem we need to find out all left leaves. A leaf is a node without child nodes. To find all left leaves we can use one of the binary traversal algorithms with a small modification, we need to track is a left leaf or not. If a leaf is a left leaf we need to update a sum
Code
public int LeftLeavesSum(TreeNode root)
{
var result = new int[1];
Sum(root, false, result);
return result[0];
}
private void Sum(TreeNode root, bool isLeft, int[] result)
{
if (root == null)
{
return;
}
if (isLeft && root.Left == null && root.Right == null)
{
result[0] += root.Value;
}
Sum(root.Left, true, result);
Sum(root.Right, false, result);
}
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