sum-of-left-leaves.go

package main

import (
	. "github.com/dimaglushkov/solutions/ADS/tree"
)

// source: https://leetcode.com/problems/sum-of-left-leaves/

/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */
func sumOfLeftLeaves(root *TreeNode) int {
	ans := 0
	var dfs func(node *TreeNode, isLeft bool)
	dfs = func(node *TreeNode, isLeft bool) {
		if node == nil {
			return
		}

		if node.Left == nil && node.Right == nil && isLeft {
			ans += node.Val
		}

		if node.Left != nil {
			dfs(node.Left, true)
		}
		if node.Right != nil {
			dfs(node.Right, false)
		}
	}
	dfs(root, false)
	return ans
}