https://github.com/yuanyu90221/range-sum-of-bst
https://github.com/yuanyu90221/range-sum-of-bst
Last synced: 8 months ago
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- Host: GitHub
- URL: https://github.com/yuanyu90221/range-sum-of-bst
- Owner: yuanyu90221
- Created: 2020-08-15T17:43:21.000Z (about 5 years ago)
- Default Branch: master
- Last Pushed: 2020-08-15T17:45:47.000Z (about 5 years ago)
- Last Synced: 2024-04-21T14:01:03.252Z (over 1 year ago)
- Language: Go
- Size: 2.93 KB
- Stars: 0
- Watchers: 3
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
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README
# range sum of bst
## 題目解讀：
### 題目來源:
[range-sum-of-bst](https://leetcode.com/problems/range-sum-of-bst/)
### 原文:
Given the root node of a binary search tree, return the sum of values of all nodes with value between L and R (inclusive).
The binary search tree is guaranteed to have unique values.
### 解讀：
給定一個二元搜尋樹root, 給兩個正整數 L跟R
求出介於L跟R之間的所有元素的和(包含L,R)
## 初步解法:
### 初步觀察:
這題的關鍵在於
要透過二元搜尋樹去traverse介於L跟R的值
所以需要理解二元搜尋樹的分佈規則：
遇到一個數值 會先放在節點
下一個遇到的數值若是比節點大 會放在節點右邊子節點
反之, 則會放在左節點
初步想法是 先紀錄 找尋到L,R的所有節點 到一個Set S
然後從L往下找可能大於的L的右subtree
從R往下找左subtree
對Set 檢查元素 把符合條件得做相加
### 初步設計:
## 遇到的困難
### 題目上理解的問題
因為英文不是筆者母語
所以在題意解讀上 容易被英文用詞解讀給搞模糊
### pseudo code撰寫
一開始不習慣把pseudo code寫下來
因此 不太容易把自己的code做解析
### golang table driven test不熟
對於table driven test還不太熟析
所以對於寫test還是耗費不少時間
## 我的github source code
```golang
package range_sum_bst
type TreeNode struct {
Val int
Left *TreeNode
Right *TreeNode
}
func rangeSumBST(root *TreeNode, L int, R int) int {
result := 0
result = transversal(root, L, R)
return result
}
func transversal(root *TreeNode, L int, R int) int {
// put unique val
count := 0
if root.Val <= R && root.Val >= L {
count += root.Val
}
if root.Left != nil && root.Val != L {
count += transversal(root.Left, L, R)
}
if root.Right != nil && root.Val != R {
count += transversal(root.Right, L, R)
}
return count
}
```
參考別人的作法
```golang
package range_sum_bst
type TreeNode struct {
Val int
Left *TreeNode
Right *TreeNode
}
func rangeSumBST(root *TreeNode, L int, R int) int {
result := 0
result = transversal(root, L, R)
return result
}
func transversal(root *TreeNode, L int, R int) int {
if root == nil {
return 0
}
switch {
case root.Val > R:
return transversal(root.Left, L, R)
case root.Val < L:
return transversal(root.Right, L, R)
default:
return transversal(root.Left, L, R) + root.Val + transversal(root.Right, L, R)
}
}
```
## 測資的撰寫
```golang
package range_sum_bst
import "testing"
func Test_rangeSumBST(t *testing.T) {
type args struct {
root *TreeNode
L int
R int
}
tests := []struct {
name string
args args
want int
}{
{
name: "Example1",
args: args{
root: &TreeNode{
Val: 10,
Left: &TreeNode{
Val: 5,
Left: &TreeNode{
Val: 3,
Left: nil,
Right: nil,
},
Right: &TreeNode{
Val: 7,
Left: nil,
Right: nil,
},
},
Right: &TreeNode{
Val: 15,
Left: nil,
Right: &TreeNode{
Val: 18,
Left: nil,
Right: nil,
},
},
},
L: 7,
R: 15,
},
want: 32,
},
{
name: "Example2",
args: args{
root: &TreeNode{
Val: 10,
Left: &TreeNode{
Val: 5,
Left: &TreeNode{
Val: 3,
Left: &TreeNode{
Val: 1,
Left: nil,
Right: nil,
},
Right: nil,
},
Right: &TreeNode{
Val: 7,
Left: &TreeNode{
Val: 6,
Left: nil,
Right: nil,
},
Right: nil,
},
},
Right: &TreeNode{
Val: 15,
Left: &TreeNode{
Val: 13,
Left: nil,
Right: nil,
},
Right: &TreeNode{
Val: 18,
Left: nil,
Right: nil,
},
},
},
L: 6,
R: 10,
},
want: 23,
},
}
for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
if got := rangeSumBST(tt.args.root, tt.args.L, tt.args.R); got != tt.want {
t.Errorf("rangeSumBST() = %v, want %v", got, tt.want)
}
})
}
}
```
## my self record
[golang leetcode 30day 16th day](https://hackmd.io/YhGZx0XfTn25Bp5ciLNB0w?view)
## 參考文章
[golang test](https://ithelp.ithome.com.tw/articles/10204692)