AC 124

hard/124.go

@@ -9,9 +9,30 @@ package main
  * }
  */
 func maxPathSum(root *TreeNode) int {
-	return 0
+	maxInt := func(x, y int) int {
+		if x > y {
+			return x
+		}
+		return y
+	}
+	var recurse func(*TreeNode) int
+	max := root.Val
+	recurse = func(root *TreeNode) int { // Sum every path bottom-up is the key
+		if root == nil {
+			return 0
+		}
+		maxL := maxInt(0, recurse(root.Left)) // 0 means do not pick the path
+		maxR := maxInt(0, recurse(root.Right))
+		max = maxInt(max, root.Val+maxL+maxR)
+		return root.Val + maxInt(maxL, maxR)
+	}
+	recurse(root)
+	return max
 }
 
-func main() {
-
-}
+// func main() {
+// 	tree := toBinaryTree(newInt(-10), newInt(9), newInt(20), nil, nil, newInt(15), newInt(7))
+// 	println(maxPathSum(tree), 42)
+// 	tree = toBinaryTree(newInt(1), newInt(2), newInt(3))
+// 	println(maxPathSum(tree), 6)
+// }

hard/126.go

@@ -0,0 +1,9 @@
+package main
+
+func findLadders(beginWord string, endWord string, wordList []string) [][]string {
+	return [][]string{}
+}
+
+func main() {
+
+}