some more problems

binary-tree-cameras/sol.go

@@ -0,0 +1,42 @@
+package main
+
+type TreeNode struct {
+	Val   int
+	Left  *TreeNode
+	Right *TreeNode
+}
+
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+func minCameraCover(root *TreeNode) int {
+	covered := map[*TreeNode]bool{
+		nil: true,
+	}
+	return dfs(root, nil, covered)
+}
+
+func dfs(node, parent *TreeNode, covered map[*TreeNode]bool) int {
+	if node != nil {
+		out := dfs(node.Left, node, covered)
+		out += dfs(node.Right, node, covered)
+
+		_, nc := covered[node]
+		_, lc := covered[node.Left]
+		_, rc := covered[node.Right]
+		if parent == nil && !nc || !lc || !rc {
+			covered[node] = true
+			covered[parent] = true
+			covered[node.Left] = true
+			covered[node.Right] = true
+			return out + 1
+		}
+		return out
+	}
+	return 0
+}