.\894.all-possible-full-binary-trees.go

侯利朋 · 侯利朋 · commit 3e55d3bef3d5 · 2019-08-28T12:36:39.000+08:00
diff --git a/894.all-possible-full-binary-trees.go b/894.all-possible-full-binary-trees.go
@@ -0,0 +1,51 @@
+/*
+ * @lc app=leetcode id=894 lang=golang
+ *
+ * [894] All Possible Full Binary Trees
+ */
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+//  432 ms, faster than 70.00%
+// 满二叉树的总结点个数规律 , 奇数节点
+func allPossibleFBT(N int) []*TreeNode {
+	// map 加速
+	m := make(map[int][]*TreeNode)
+	return FBT(N, m)
+}
+
+func FBT(N int, m map[int][]*TreeNode) []*TreeNode {
+	if v, ok := m[N]; ok {
+		return v
+	}
+	rtn := []*TreeNode{}
+	if N == 1 {
+		rtn = append(rtn, &TreeNode{
+			Val:   0,
+			Left:  nil,
+			Right: nil,
+		})
+	} else if N&1 != 0 {
+		for x := 0; x < N; x++ {
+			y := N - 1 - x
+			tree := &TreeNode{}
+			tree.Val = 0
+			for _, ltree := range FBT(x, m) {
+				for _, rtree := range FBT(y, m) {
+					rtn = append(rtn, &TreeNode{
+						Val:   0,
+						Left:  ltree,
+						Right: rtree,
+					})
+				}
+			}
+		}
+	}
+	m[N] = rtn
+	return rtn
+}
