Merge pull request #1265 from 0xff-dev/1948

Add solution and test-cases for problem 1948

Author: 6boris

leetcode/1901-2000/1948.Delete-Duplicate-Folders-in-System/1.jpg

@@ -1,28 +1,63 @@
 # [1948.Delete Duplicate Folders in System][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
+Due to a bug, there are many duplicate folders in a file system. You are given a 2D array `paths`, where `paths[i]` is an array representing an absolute path to the `ith` folder in the file system.
+
+- For example, `["one", "two", "three"]` represents the path `"/one/two/three"`.
+
+Two folders (not necessarily on the same level) are **identical** if they contain the **same non-empty** set of identical subfolders and underlying subfolder structure. The folders **do not** need to be at the root level to be identical. If two or more folders are **identical**, then **mark** the folders as well as all their subfolders.
+
+- For example, folders `"/a"` and `"/b"` in the file structure below are identical. They (as well as their subfolders) should **all** be marked:
+
+- `/a`
+- `/a/x`
+- `/a/x/y`
+- `/a/z`
+- `/b`
+- `/b/x`
+- `/b/x/y`
+- `/b/z`
+
+- However, if the file structure also included the path `"/b/w"`, then the folders `"/a"` and `"/b"` would not be identical. Note that `"/a/x"` and `"/b/x"` would still be considered identical even with the added folder.
+
+Once all the identical folders and their subfolders have been marked, the file system will **delete** all of them. The file system only runs the deletion once, so any folders that become identical after the initial deletion are not deleted.
 
-**Example 1:**
+Return the 2D array `ans` containing the paths of the **remaining** folders after deleting all the marked folders. The paths may be returned in **any** order.
+
+**Example 1:**  
+
+![1](./1.jpg)
 
 ```
-Input: a = "11", b = "1"
-Output: "100"
+Input: paths = [["a"],["c"],["d"],["a","b"],["c","b"],["d","a"]]
+Output: [["d"],["d","a"]]
+Explanation: The file structure is as shown.
+Folders "/a" and "/c" (and their subfolders) are marked for deletion because they both contain an empty
+folder named "b".
 ```
 
-## 题意
-> ...
+**Example 2:**  
 
-## 题解
+![2](./2.jpg)
 
-### 思路1
-> ...
-Delete Duplicate Folders in System
-```go
 ```
+Input: paths = [["a"],["c"],["a","b"],["c","b"],["a","b","x"],["a","b","x","y"],["w"],["w","y"]]
+Output: [["c"],["c","b"],["a"],["a","b"]]
+Explanation: The file structure is as shown. 
+Folders "/a/b/x" and "/w" (and their subfolders) are marked for deletion because they both contain an empty folder named "y".
+Note that folders "/a" and "/c" are identical after the deletion, but they are not deleted because they were not marked beforehand.
+```
+
+**Example 3:**  
 
+![3](./3.jpg)
+
+```
+Input: paths = [["a","b"],["c","d"],["c"],["a"]]
+Output: [["c"],["c","d"],["a"],["a","b"]]
+Explanation: All folders are unique in the file system.
+Note that the returned array can be in a different order as the order does not matter.
+```
 
 ## 结语
 

leetcode/1901-2000/1948.Delete-Duplicate-Folders-in-System/2.jpg

@@ -1,5 +1,108 @@
 package Solution
 
-func Solution(x bool) bool {
-	return x
+import (
+	"fmt"
+	"sort"
+	"strings"
+)
+
+type Tree struct {
+	Value      string
+	ValueIndex map[string]int
+	Children   []*Tree
+	Del        bool
+}
+
+func Solution(paths [][]string) [][]string {
+	sort.Slice(paths, func(i, j int) bool {
+		a, b := len(paths[i]), len(paths[j])
+		l := min(a, b)
+		for k := range l {
+			if paths[i][k] != paths[j][k] {
+				return paths[i][k] < paths[j][k]
+			}
+		}
+		return a < b
+	})
+	// 将所有的子目录序列化成一个字符串。之前有过这样的题，搞成字符串
+	root := &Tree{Value: "/", Children: []*Tree{}, ValueIndex: map[string]int{}}
+	var buildTree func([]string)
+	buildTree = func(p []string) {
+		walker := root
+		for _, sub := range p {
+			index, ok := walker.ValueIndex[sub]
+			if ok {
+				walker = walker.Children[index]
+				continue
+			}
+			tree := &Tree{
+				Value: sub, Children: []*Tree{}, ValueIndex: map[string]int{},
+			}
+			walker.Children = append(walker.Children, tree)
+			walker.ValueIndex[sub] = len(walker.Children) - 1
+			walker = tree
+		}
+	}
+	for _, path := range paths {
+		buildTree(path)
+	}
+
+	var buildNodeFlag func(*Tree) string
+
+	pathToNode := map[string][]*Tree{}
+	buildNodeFlag = func(node *Tree) string {
+		if node == nil {
+			return "#"
+		}
+		if len(node.Children) == 0 {
+			return node.Value + "#"
+		}
+		sb := strings.Builder{}
+		for i, c := range node.Children {
+			tmp := buildNodeFlag(c) + fmt.Sprintf("%d", i)
+			sb.WriteString(tmp)
+		}
+		s := sb.String()
+		pathToNode[s] = append(pathToNode[s], node)
+		return node.Value + s
+	}
+	buildNodeFlag(root)
+	for path, nodes := range pathToNode {
+		if len(path) == 0 {
+			continue
+		}
+		if len(nodes) > 1 {
+			// 有重复的
+			for _, n := range nodes {
+				n.Del = true
+			}
+		}
+	}
+	var filterPath func([]string) []string
+	filterPath = func(cur []string) []string {
+		walker := root
+		i := 0
+		for ; i < len(cur); i++ {
+			index := walker.ValueIndex[cur[i]]
+			if walker.Children[index].Del {
+				break
+			}
+			walker = walker.Children[index]
+		}
+		return cur[:i]
+	}
+	in := map[string]struct{}{}
+	var ans [][]string
+	for _, path := range paths {
+		res := filterPath(path)
+		if len(res) > 0 {
+			key := strings.Join(res, "/")
+			if _, ok := in[key]; ok {
+				continue
+			}
+			ans = append(ans, res)
+			in[key] = struct{}{}
+		}
+	}
+	return ans
 }

leetcode/1901-2000/1948.Delete-Duplicate-Folders-in-System/3.jpg

@@ -10,12 +10,25 @@ func TestSolution(t *testing.T) {
 	//	测试用例
 	cases := []struct {
 		name   string
-		inputs bool
-		expect bool
+		inputs [][]string
+		expect [][]string
 	}{
-		{"TestCase", true, true},
-		{"TestCase", true, true},
-		{"TestCase", false, false},
+		{"TestCase1", [][]string{
+			{"a"}, {"c"}, {"d"}, {"a", "b"},
+			{"c", "b"}, {"d", "a"},
+		}, [][]string{{"d"}, {"d", "a"}}},
+		{"TestCase2", [][]string{
+			{"a"}, {"c"}, {"a", "b"}, {"c", "b"}, {"a", "b", "x"},
+			{"a", "b", "x", "y"}, {"w"}, {"w", "y"},
+		}, [][]string{
+			{"a"}, {"a", "b"},
+			{"c"}, {"c", "b"},
+		}},
+		{"TestCase3", [][]string{
+			{"a", "b"}, {"c", "d"}, {"c"}, {"a"},
+		}, [][]string{
+			{"a"}, {"a", "b"}, {"c"}, {"c", "d"},
+		}},
 	}
 
 	//	开始测试
@@ -30,10 +43,10 @@ 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() {
 }