Merge pull request #593 from 0xff-dev/2471

Add solution and test-cases for problem 2471

leetcode/2401-2500/2471.Minimum-Number-of-Operations-to-Sort-a-Binary-Tree-by-Level/README.md

@@ -1,28 +1,53 @@
 # [2471.Minimum Number of Operations to Sort a Binary Tree by Level][title]
 
-> [!WARNING|style:flat]
-> This question is temporarily unanswered if you have good ideas. Welcome to [Create Pull Request PR](https://github.com/kylesliu/awesome-golang-algorithm)
-
 ## Description
+You are given the `root` of a binary tree with **unique values**.
+
+In one operation, you can choose any two nodes **at the same level** and swap their values.
+
+Return the minimum number of operations needed to make the values at each level sorted in a **strictly increasing order**.
+
+The **level** of a node is the number of edges along the path between it and the root node.
+
+**Example 1:**  
 
-**Example 1:**
+![example1](./1.png)
 
 ```
-Input: a = "11", b = "1"
-Output: "100"
+Input: root = [1,4,3,7,6,8,5,null,null,null,null,9,null,10]
+Output: 3
+Explanation:
+- Swap 4 and 3. The 2nd level becomes [3,4].
+- Swap 7 and 5. The 3rd level becomes [5,6,8,7].
+- Swap 8 and 7. The 3rd level becomes [5,6,7,8].
+We used 3 operations so return 3.
+It can be proven that 3 is the minimum number of operations needed.
 ```
 
-## 题意
-> ...
+**Example 2:**  
 
-## 题解
+![example2](./2.png)
 
-### 思路1
-> ...
-Minimum Number of Operations to Sort a Binary Tree by Level
-```go
 ```
+Input: root = [1,3,2,7,6,5,4]
+Output: 3
+Explanation:
+- Swap 3 and 2. The 2nd level becomes [2,3].
+- Swap 7 and 4. The 3rd level becomes [4,6,5,7].
+- Swap 6 and 5. The 3rd level becomes [4,5,6,7].
+We used 3 operations so return 3.
+It can be proven that 3 is the minimum number of operations needed.
+```
+
+**Example 3:**  
+
+![example3](./3.png)
 
+```
+Input: root = [1,2,3,4,5,6]
+Output: 0
+Explanation: Each level is already sorted in increasing order so return 0.
+```
 
 ## 结语
 

leetcode/2401-2500/2471.Minimum-Number-of-Operations-to-Sort-a-Binary-Tree-by-Level/Solution.go

@@ -1,5 +1,65 @@
 package Solution
 
-func Solution(x bool) bool {
-	return x
+import (
+	"sort"
+)
+
+type TreeNode struct {
+	Val         int
+	Left, Right *TreeNode
+}
+
+func minimumCostSort(nums []int) int {
+	b := make([]int, len(nums))
+	rightPos := make(map[int]int)
+	copy(b, nums)
+	sort.Ints(b)
+	for i, n := range b {
+		rightPos[n] = i
+	}
+	swapCount := 0
+	idx := 0
+	for idx < len(nums) {
+		if nums[idx] == b[idx] {
+			idx++
+			continue
+		}
+		correctPos := rightPos[nums[idx]]
+		nums[idx], nums[correctPos] = nums[correctPos], nums[idx]
+		swapCount++
+
+	}
+	/*
+		for idx := 0; idx < len(nums); idx++ {
+			if nums[idx] == b[idx] {
+				continue
+			}
+			correctPos := rightPos[nums[idx]]
+			nums[idx], nums[correctPos] = nums[correctPos], nums[idx]
+			swapCount++
+		}
+	*/
+	return swapCount
+}
+
+func Solution(root *TreeNode) int {
+	ans := 0
+	queue := []*TreeNode{root}
+	for len(queue) > 0 {
+		next := make([]*TreeNode, 0)
+		values := make([]int, 0)
+		for _, item := range queue {
+			if item.Left != nil {
+				next = append(next, item.Left)
+				values = append(values, item.Left.Val)
+			}
+			if item.Right != nil {
+				next = append(next, item.Right)
+				values = append(values, item.Right.Val)
+			}
+		}
+		ans += minimumCostSort(values)
+		queue = next
+	}
+	return ans
 }

leetcode/2401-2500/2471.Minimum-Number-of-Operations-to-Sort-a-Binary-Tree-by-Level/Solution_test.go

@@ -10,12 +10,52 @@ func TestSolution(t *testing.T) {
 	//	测试用例
 	cases := []struct {
 		name   string
-		inputs bool
-		expect bool
+		inputs *TreeNode
+		expect int
 	}{
-		{"TestCase", true, true},
-		{"TestCase", true, true},
-		{"TestCase", false, false},
+		{"TestCase1", &TreeNode{
+			Val: 1,
+			Left: &TreeNode{
+				Val:   4,
+				Left:  &TreeNode{Val: 7},
+				Right: &TreeNode{Val: 6},
+			},
+			Right: &TreeNode{
+				Val: 3,
+				Left: &TreeNode{
+					Val:  8,
+					Left: &TreeNode{Val: 9},
+				},
+				Right: &TreeNode{Val: 5, Left: &TreeNode{Val: 10}},
+			},
+		}, 3},
+		{"TestCase2", &TreeNode{
+			Val: 1,
+			Left: &TreeNode{
+				Val:   3,
+				Left:  &TreeNode{Val: 7},
+				Right: &TreeNode{Val: 6},
+			},
+			Right: &TreeNode{
+				Val: 2,
+				Left: &TreeNode{
+					Val: 5,
+				},
+				Right: &TreeNode{Val: 4},
+			},
+		}, 3},
+		{"TestCase3", &TreeNode{
+			Val: 1,
+			Left: &TreeNode{
+				Val:   2,
+				Left:  &TreeNode{Val: 4},
+				Right: &TreeNode{Val: 5},
+			},
+			Right: &TreeNode{
+				Val:  3,
+				Left: &TreeNode{Val: 6},
+			},
+		}, 0},
 	}
 
 	//	开始测试
@@ -30,10 +70,10 @@ func TestSolution(t *testing.T) {
 	}
 }
 
-//	压力测试
+// 压力测试
 func BenchmarkSolution(b *testing.B) {
 }
 
-//	使用案列
+// 使用案列
 func ExampleSolution() {
 }