Skip to content

Navigation Menu

Sign in
Appearance settings

Search code, repositories, users, issues, pull requests...

Provide feedback

We read every piece of feedback, and take your input very seriously.

Saved searches

Use saved searches to filter your results more quickly
Sign up
Appearance settings

Commit dbacdf4

Browse files
add: Course Schedule II
1 parent 09b5f38 commit dbacdf4

File tree

3 files changed

+95
-0
lines changed

3 files changed

+95
-0
lines changed

‎README.md‎

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -50,6 +50,7 @@ This is the solutions collection of my LeetCode submissions, most of them are pr
5050
|197|[Rising Temperature](https://leetcode.com/problems/rising-temperature/) | [SQL](./src/rising-temperature/res.txt)|Easy|
5151
|206|[Reverse Linked List](https://leetcode.com/problems/reverse-linked-list/) | [JavaScript](./src/reverse-linked-list/res.js)|Easy|
5252
|207|[Course Schedule](https://leetcode.com/problems/course-schedule/) | [JavaScript](./src/course-schedule/res.js)|Medium|
53+
|210|[Course Schedule II](https://leetcode.com/problems/course-schedule-ii/) | [JavaScript](./src/course-schedule-ii/res.js)|Medium|
5354
|240|[Search a 2D Matrix II](https://leetcode.com/problems/search-a-2d-matrix-ii/) | [JavaScript](./src/search-a-2d-matrix-ii/res.js)|Medium|
5455
|307|[Range Sum Query - Mutable](https://leetcode.com/problems/range-sum-query-mutable/) | [JavaScript](./src/range-sum-query-mutable/res.js)|Medium|
5556
|342|[Power of Four](https://leetcode.com/problems/power-of-four/) | [JavaScript](./src/power-of-four/res.js)|Easy|

‎src/course-schedule-ii/res.js‎

Lines changed: 92 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,92 @@
1+
/**
2+
* res.js
3+
* @authors Joe Jiang (hijiangtao@gmail.com)
4+
* @date 2017年04月17日 10:46:36
5+
*
6+
* There are a total of n courses you have to take, labeled from 0 to n - 1.
7+
*
8+
* Some courses may have prerequisites, for example to take course 0 you have to first take course 1, which is expressed as a pair: [0,1]
9+
*
10+
* Given the total number of courses and a list of prerequisite pairs, is it possible for you to finish all courses?
11+
*
12+
* For example:
13+
*
14+
* 2, [[1,0]]
15+
* There are a total of 2 courses to take. To take course 1 you should have finished course 0. So it is possible.
16+
*
17+
* 4, [[1,0],[2,0],[3,1],[3,2]]
18+
* There are a total of 4 courses to take. To take course 3 you should have finished both courses 1 and 2. Both courses 1 and 2 should be taken after you finished course 0. So one correct course order is [0,1,2,3]. Another correct ordering is[0,2,1,3].
19+
*
20+
* Tips: Otherwise, you should return []
21+
*
22+
* @param {number} numCourses
23+
* @param {number[][]} prerequisites
24+
* @return {number[]}
25+
*/
26+
let findOrder = function(numCourses, prerequisites) {
27+
let prelen = prerequisites.length,
28+
maxNoCircle = numCourses * (numCourses - 1) / 2;
29+
// 当所有点都有边连接时, 最大的无环边数
30+
if (prelen > maxNoCircle) {
31+
return [];
32+
}
33+
34+
let queue = [], // 存储 BFS 待访问节点序列
35+
flags = [], // 存储节点是否被访问过的标记
36+
res = [], //结果
37+
nodedegree = new Array(numCourses), // 存储node的连边总数
38+
edges = new Array(numCourses); // 存储连边信息, 每个元素中存储的数组表示自己的后续课程
39+
for (let i = 0; i < numCourses; i++) {
40+
flags[i] = false;
41+
nodedegree[i] = 0;
42+
edges[i] = [];
43+
}
44+
45+
for (let i = 0; i < prelen; i++) {
46+
let source = prerequisites[i][0],
47+
target = prerequisites[i][1];
48+
49+
edges[target].push(source);
50+
nodedegree[source]++;
51+
nodedegree[target]++;
52+
}
53+
54+
for (let i = 0; i < numCourses; i++) {
55+
if (nodedegree[i] === edges[i].length) {
56+
queue.push(i);
57+
}
58+
}
59+
60+
if (bfsVisit()) {
61+
return res;
62+
} else {
63+
return [];
64+
}
65+
66+
function bfsVisit() {
67+
while (queue.length) {
68+
let current = queue.shift(), //当前访问节点
69+
elen = edges[current].length; // 边数
70+
71+
res.push(current);
72+
// console.log(current, res);
73+
flags[current] = true;
74+
for (let i=0; i<elen; i++) {
75+
let target = edges[current][i];
76+
if (flags[target]) {
77+
return false; // 有回路,返回 false
78+
}
79+
if (--nodedegree[target] === edges[target].length) {
80+
queue.push(target);
81+
}
82+
}
83+
edges[current] = [];
84+
nodedegree[current] -= elen;
85+
}
86+
87+
if (res.length < numCourses) {
88+
return false;
89+
}
90+
return true;
91+
}
92+
};

‎src/course-schedule/res.js‎

Lines changed: 2 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -2,6 +2,8 @@
22
* res.js
33
* @authors Joe Jiang (hijiangtao@gmail.com)
44
* @date 2017年04月17日 00:09:34
5+
*
6+
* Topological sorting: https://en.wikipedia.org/wiki/Topological_sorting
57
*
68
* There are a total of n courses you have to take, labeled from 0 to n - 1.
79
*

0 commit comments

Comments
(0)

AltStyle によって変換されたページ (->オリジナル) /