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feat: add solutions to lc problem: No.0802.Find Eventual Safe States
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Diff for: ‎solution/0800-0899/0802.Find Eventual Safe States/README.md

+93-1
Original file line numberDiff line numberDiff line change
@@ -53,22 +53,114 @@
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<!-- 这里可写通用的实现逻辑 -->
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出度为零的点是安全的，如果一个点**只能**到达安全的点，那么它同样是安全的，所以问题转换成了拓扑排序
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<!-- tabs:start -->
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### **Python3**
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<!-- 这里可写当前语言的特殊实现逻辑 -->
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```python
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class Solution:
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def eventualSafeNodes(self, graph: List[List[int]]) -> List[int]:
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n = len(graph)
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outDegree = [len(vs) for vs in graph]
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revGraph = [[] for _ in range(n)]
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for u, vs in enumerate(graph):
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for v in vs:
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revGraph[v].append(u)
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q = deque([i for i, d in enumerate(outDegree) if d == 0])
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while q:
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for u in revGraph[q.popleft()]:
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outDegree[u] -= 1
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if outDegree[u] == 0:
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q.append(u)
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return [i for i, d in enumerate(outDegree) if d == 0]
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```
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### **Java**
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<!-- 这里可写当前语言的特殊实现逻辑 -->
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```java
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class Solution {
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public List<Integer> eventualSafeNodes(int[][] graph) {
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int n = graph.length;
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int[] outDegrees = new int[n];
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Queue<Integer> queue = new ArrayDeque<>();
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List<List<Integer>> revGraph = new ArrayList<>();
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for (int i = 0; i < n; i++) {
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revGraph.add(new ArrayList<>());
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}
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for (int u = 0; u < n; u++) {
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for (int v : graph[u]) {
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revGraph.get(v).add(u);
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}
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outDegrees[u] = graph[u].length;
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if (outDegrees[u] == 0) {
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queue.offer(u);
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}
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}
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while (!queue.isEmpty()) {
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int v = queue.poll();
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for (int u : revGraph.get(v)) {
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if (--outDegrees[u] == 0) {
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queue.offer(u);
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}
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}
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}
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List<Integer> ans = new ArrayList<>();
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for (int i = 0; i < n; i++) {
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if (outDegrees[i] == 0) {
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ans.add(i);
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}
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}
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return ans;
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}
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}
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```
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### **Go**
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```go
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func eventualSafeNodes(graph [][]int) []int {
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n := len(graph)
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outDegree := make([]int, n)
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revGraph := make([][]int, n)
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queue := make([]int, 0)
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ans := make([]int, 0)
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for u, vs := range graph {
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for _, v := range vs {
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revGraph[v] = append(revGraph[v], u)
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}
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outDegree[u] = len(vs)
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if outDegree[u] == 0 {
142+
queue = append(queue, u)
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}
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}
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for len(queue) > 0 {
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v := queue[0]
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queue = queue[1:]
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for _, u := range revGraph[v] {
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outDegree[u]--
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if outDegree[u] == 0 {
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queue = append(queue, u)
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}
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}
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}
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for i, d := range outDegree {
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if d == 0 {
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ans = append(ans, i)
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}
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}
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return ans
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}
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```
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### **...**

Diff for: ‎solution/0800-0899/0802.Find Eventual Safe States/README_EN.md

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Original file line numberDiff line numberDiff line change
@@ -43,18 +43,110 @@
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## Solutions
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The point with zero out-degree is safe, and if a point can **only** reach the safe point, then it is also safe, so the problem can be converted to topological sorting.
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<!-- tabs:start -->
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### **Python3**
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```python
51-
53+
class Solution:
54+
def eventualSafeNodes(self, graph: List[List[int]]) -> List[int]:
55+
n = len(graph)
56+
outDegree = [len(vs) for vs in graph]
57+
revGraph = [[] for _ in range(n)]
58+
for u, vs in enumerate(graph):
59+
for v in vs:
60+
revGraph[v].append(u)
61+
q = deque([i for i, d in enumerate(outDegree) if d == 0])
62+
while q:
63+
for u in revGraph[q.popleft()]:
64+
outDegree[u] -= 1
65+
if outDegree[u] == 0:
66+
q.append(u)
67+
return [i for i, d in enumerate(outDegree) if d == 0]
5268
```
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5470
### **Java**
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```java
73+
class Solution {
74+
public List<Integer> eventualSafeNodes(int[][] graph) {
75+
int n = graph.length;
76+
int[] outDegrees = new int[n];
77+
Queue<Integer> queue = new ArrayDeque<>();
78+
List<List<Integer>> revGraph = new ArrayList<>();
79+
for (int i = 0; i < n; i++) {
80+
revGraph.add(new ArrayList<>());
81+
}
82+
for (int u = 0; u < n; u++) {
83+
for (int v : graph[u]) {
84+
revGraph.get(v).add(u);
85+
}
86+
outDegrees[u] = graph[u].length;
87+
if (outDegrees[u] == 0) {
88+
queue.offer(u);
89+
}
90+
}
91+
92+
while (!queue.isEmpty()) {
93+
int v = queue.poll();
94+
for (int u : revGraph.get(v)) {
95+
if (--outDegrees[u] == 0) {
96+
queue.offer(u);
97+
}
98+
}
99+
}
100+
101+
List<Integer> ans = new ArrayList<>();
102+
for (int i = 0; i < n; i++) {
103+
if (outDegrees[i] == 0) {
104+
ans.add(i);
105+
}
106+
}
107+
return ans;
108+
}
109+
}
110+
```
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112+
### **Go**
113+
114+
```go
115+
func eventualSafeNodes(graph [][]int) []int {
116+
n := len(graph)
117+
outDegree := make([]int, n)
118+
revGraph := make([][]int, n)
119+
queue := make([]int, 0)
120+
ans := make([]int, 0)
121+
122+
for u, vs := range graph {
123+
for _, v := range vs {
124+
revGraph[v] = append(revGraph[v], u)
125+
}
126+
outDegree[u] = len(vs)
127+
if outDegree[u] == 0 {
128+
queue = append(queue, u)
129+
}
130+
}
131+
132+
for len(queue) > 0 {
133+
v := queue[0]
134+
queue = queue[1:]
135+
for _, u := range revGraph[v] {
136+
outDegree[u]--
137+
if outDegree[u] == 0 {
138+
queue = append(queue, u)
139+
}
140+
}
141+
}
142+
143+
for i, d := range outDegree {
144+
if d == 0 {
145+
ans = append(ans, i)
146+
}
147+
}
148+
return ans
149+
}
58150
```
59151

60152
### **...**

Diff for: ‎solution/0800-0899/0802.Find Eventual Safe States/Solution.go

+35
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,35 @@
1+
func eventualSafeNodes(graph [][]int) []int {
2+
n := len(graph)
3+
outDegree := make([]int, n)
4+
revGraph := make([][]int, n)
5+
queue := make([]int, 0)
6+
ans := make([]int, 0)
7+
8+
for u, vs := range graph {
9+
for _, v := range vs {
10+
revGraph[v] = append(revGraph[v], u)
11+
}
12+
outDegree[u] = len(vs)
13+
if outDegree[u] == 0 {
14+
queue = append(queue, u)
15+
}
16+
}
17+
18+
for len(queue) > 0 {
19+
v := queue[0]
20+
queue = queue[1:]
21+
for _, u := range revGraph[v] {
22+
outDegree[u]--
23+
if outDegree[u] == 0 {
24+
queue = append(queue, u)
25+
}
26+
}
27+
}
28+
29+
for i, d := range outDegree {
30+
if d == 0 {
31+
ans = append(ans, i)
32+
}
33+
}
34+
return ans
35+
}

Diff for: ‎solution/0800-0899/0802.Find Eventual Safe States/Solution.java

+37
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,37 @@
1+
class Solution {
2+
public List<Integer> eventualSafeNodes(int[][] graph) {
3+
int n = graph.length;
4+
int[] outDegrees = new int[n];
5+
Queue<Integer> queue = new ArrayDeque<>();
6+
List<List<Integer>> revGraph = new ArrayList<>();
7+
for (int i = 0; i < n; i++) {
8+
revGraph.add(new ArrayList<>());
9+
}
10+
for (int u = 0; u < n; u++) {
11+
for (int v : graph[u]) {
12+
revGraph.get(v).add(u);
13+
}
14+
outDegrees[u] = graph[u].length;
15+
if (outDegrees[u] == 0) {
16+
queue.offer(u);
17+
}
18+
}
19+
20+
while (!queue.isEmpty()) {
21+
int v = queue.poll();
22+
for (int u : revGraph.get(v)) {
23+
if (--outDegrees[u] == 0) {
24+
queue.offer(u);
25+
}
26+
}
27+
}
28+
29+
List<Integer> ans = new ArrayList<>();
30+
for (int i = 0; i < n; i++) {
31+
if (outDegrees[i] == 0) {
32+
ans.add(i);
33+
}
34+
}
35+
return ans;
36+
}
37+
}

Diff for: ‎solution/0800-0899/0802.Find Eventual Safe States/Solution.py

+19
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,19 @@
1+
from typing import List
2+
from collections import deque
3+
4+
5+
class Solution:
6+
def eventualSafeNodes(self, graph: List[List[int]]) -> List[int]:
7+
n = len(graph)
8+
outDegree = [len(vs) for vs in graph]
9+
revGraph = [[] for _ in range(n)]
10+
for u, vs in enumerate(graph):
11+
for v in vs:
12+
revGraph[v].append(u)
13+
q = deque([i for i, d in enumerate(outDegree) if d == 0])
14+
while q:
15+
for u in revGraph[q.popleft()]:
16+
outDegree[u] -= 1
17+
if outDegree[u] == 0:
18+
q.append(u)
19+
return [i for i, d in enumerate(outDegree) if d == 0]

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