@@ -61,22 +61,22 @@ class Solution:
6161 def canFinish (self numCourses : int , prerequisites : List[List[int ]]) -> bool :
6262 edges = defaultdict(list )
6363 indegree = [0 ] * numCourses
64- for i, j in prerequisites:
65- edges[j ].append(i )
66- indegree[i ] += 1
64+ for a, b in prerequisites:
65+ edges[b ].append(a )
66+ indegree[a ] += 1
6767 q = deque()
6868 for i in range (numCourses):
6969 if indegree[i] == 0 :
7070 q.append(i)
71- cnt = 0
71+ n = 0
7272 while q:
73- i = q.popleft()
74- cnt += 1
75- for j in edges[i ]:
76- indegree[j ] -= 1
77- if indegree[j ] == 0 :
78- q.append(j )
79- return cnt == numCourses
73+ b = q.popleft()
74+ n += 1
75+ for a in edges[b ]:
76+ indegree[a ] -= 1
77+ if indegree[a ] == 0 :
78+ q.append(a )
79+ return n == numCourses
8080```
8181
8282### ** Java**
@@ -92,27 +92,27 @@ class Solution {
9292 }
9393 int [] indegree = new int [numCourses];
9494 for (int [] p : prerequisites) {
95- edges[p[1 ]]. add(p[0 ]);
96- ++ indegree[p[0 ]];
95+ int a = p[0 ], b = p[1 ];
96+ edges[b]. add(a);
97+ ++ indegree[a];
9798 }
9899 Queue<Integer > q = new LinkedList<> ();
99100 for (int i = 0 ; i < numCourses; ++ i) {
100101 if (indegree[i] == 0 ) {
101102 q. offer(i);
102103 }
103104 }
104- int cnt = 0 ;
105+ int n = 0 ;
105106 while (! q. isEmpty()) {
106- int i = q. poll();
107- ++ cnt;
108- for (int j : edges[i]) {
109- -- indegree[j];
110- if (indegree[j] == 0 ) {
111- q. offer(j);
107+ int b = q. poll();
108+ ++ n;
109+ for (int a : edges[b]) {
110+ if (-- indegree[a] == 0 ) {
111+ q. offer(a);
112112 }
113113 }
114114 }
115- return cnt == numCourses;
115+ return n == numCourses;
116116 }
117117}
118118```
@@ -159,29 +159,27 @@ public:
159159 bool canFinish(int numCourses, vector<vector<int >>& prerequisites) {
160160 vector<vector<int >> edges(numCourses);
161161 vector<int > indegree(numCourses);
162- for (auto p : prerequisites)
162+ for (auto& p : prerequisites)
163163 {
164- edges[ p[ 1]] .push_back(p[ 0] );
165- ++indegree[ p[ 0]] ;
164+ int a = p[ 0] , b = p[ 1] ;
165+ edges[ b] .push_back(a);
166+ ++indegree[ a] ;
166167 }
167168 queue<int > q;
168169 for (int i = 0; i < numCourses; ++i)
169- {
170- if (indegree[ i] == 0) q.push(i);
171- }
172- int cnt = 0;
170+ if (indegree[ i] == 0)
171+ q.push(i);
172+ int n = 0;
173173 while (!q.empty())
174174 {
175- int i = q.front();
175+ int b = q.front();
176176 q.pop();
177- ++cnt;
178- for (int j : edges[ i] )
179- {
180- --indegree[ j] ;
181- if (indegree[ j] == 0) q.push(j);
182- }
177+ ++n;
178+ for (int a : edges[ b] )
179+ if (--indegree[ a] == 0)
180+ q.push(a);
183181 }
184- return cnt == numCourses;
182+ return n == numCourses;
185183 }
186184};
187185```
@@ -193,76 +191,66 @@ func canFinish(numCourses int, prerequisites [][]int) bool {
193191 edges := make([][]int, numCourses)
194192 indegree := make([]int, numCourses)
195193 for _, p := range prerequisites {
196- edges[p[1]] = append(edges[p[1]], p[0])
197- indegree[p[0]]++
194+ a, b := p[0], p[1]
195+ edges[b] = append(edges[b], a)
196+ indegree[a]++
198197 }
199198 var q []int
200199 for i := 0; i < numCourses; i++ {
201200 if indegree[i] == 0 {
202201 q = append(q, i)
203202 }
204203 }
205- cnt := 0
204+ n := 0
206205 for len(q) > 0 {
207- i := q[0]
206+ b := q[0]
208207 q = q[1:]
209- cnt ++
210- for _, j := range edges[i ] {
211- indegree[j ]--
212- if indegree[j ] == 0 {
213- q = append(q, j )
208+ n ++
209+ for _, a := range edges[b ] {
210+ indegree[a ]--
211+ if indegree[a ] == 0 {
212+ q = append(q, a )
214213 }
215214 }
216215 }
217- return cnt == numCourses
216+ return n == numCourses
218217}
219218```
220219
221220### ** C#**
222221
223222``` cs
224- using System .Collections .Generic ;
225- 226223public class Solution {
227224 public bool CanFinish (int numCourses , int [][] prerequisites ) {
225+ var edges = new List <int >[numCourses ];
226+ for (int i = 0 ; i < numCourses ; ++ i )
227+ {
228+ edges [i ] = new List <int >();
229+ }
228230 var indegree = new int [numCourses ];
229- var edgeCount = prerequisites .Length ;
230- var edge = new List <int >[numCourses ];
231- for (var i = 0 ; i < edgeCount ; ++ i )
231+ for (int i = 0 ; i < prerequisites .Length ; ++ i )
232232 {
233- var child = prerequisites [i ][0 ];
234- var parent = prerequisites [i ][1 ];
235- if (edge [parent ] == null )
236- {
237- edge [parent ] = new List <int >();
238- }
239- edge [parent ].Add (child );
240- ++ indegree [child ];
233+ int a = prerequisites [i ][0 ];
234+ int b = prerequisites [i ][1 ];
235+ edges [b ].Add (a );
236+ ++ indegree [a ];
241237 }
242- 243- var queue = new Queue <int >();
244- for (var i = 0 ; i < numCourses ; ++ i )
238+ var q = new Queue <int >();
239+ for (int i = 0 ; i < numCourses ; ++ i )
245240 {
246- if (indegree [i ] == 0 ) queue .Enqueue (i );
241+ if (indegree [i ] == 0 ) q .Enqueue (i );
247242 }
248- 249- var count = 0 ;
250- while (queue .Count > 0 )
243+ var n = 0 ;
244+ while (q .Count > 0 )
251245 {
252- var node = queue .Dequeue ();
253- ++ count ;
254- if ( edge [ node ] != null )
246+ int b = q .Dequeue ();
247+ ++ n ;
248+ foreach ( int a in edges [ b ] )
255249 {
256- foreach (var next in edge [node ])
257- {
258- if (-- indegree [next ] == 0 )
259- {
260- queue .Enqueue (next );
261- }
262- }
250+ if (-- indegree [a ] == 0 ) q .Enqueue (a );
263251 }
264252 }
265- return count == numCourses ;
253+ return n == numCourses ;
266254 }
267255}
268256```
0 commit comments