Course Schedule(leetcode)
来源:互联网 发布:苹果自动拨号软件 编辑:程序博客网 时间:2024/05/22 13:52
Course Schedule
- Course Schedule
- 题目
- 解决
题目
leetcode题目
There are a total of n courses you have to take, labeled from 0
to n - 1
.
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]
Given the total number of courses and a list of prerequisite pairs, is it possible for you to finish all courses?
For example:
2, [[1,0]]
There are a total of 2 courses to take. To take course 1 you should have finished course 0. So it is possible.
2, [[1,0],[0,1]]
There are a total of 2 courses to take. To take course 1 you should have finished course 0, and to take course 0 you should also have finished course 1. So it is impossible.
Note:
- The input prerequisites is a graph represented by a list of edges, not adjacency matrices. Read more about how a graph is represented.
- You may assume that there are no duplicate edges in the input prerequisites.
解决
求图的拓扑排序。
class Solution {public: bool canFinish(int numCourses, vector<pair<int, int>>& prerequisites) { vector<unordered_set<int>> graph = makeGraph(numCourses, prerequisites); vector<int> degrees = computeIndegree(graph); for (int i = 0; i < numCourses; i++) { int temp = 0; for (; temp < numCourses; temp++) { if (degrees[temp] == 0) break; } if (temp == numCourses) { return false; } degrees[temp]= -1; for (unordered_set<int>::iterator it = graph[temp].begin(); it != graph[temp].end(); it++) { degrees[*it]--; } } return true; } vector<unordered_set<int>> makeGraph(int n, vector<pair<int, int>>& edges) { vector<unordered_set<int>> result(n); int num = edges.size(); for (int i = 0; i < num; i++) { result[edges[i].second].insert(edges[i].first); } return result; } vector<int> computeIndegree(vector<unordered_set<int>> graph) { int num = graph.size(); vector<int> result(num, 0); for (int i = 0; i < num; i++) { for (unordered_set<int>::iterator it = graph[i].begin(); it != graph[i].end(); it++) { result[*it]++; } } return result; }};
阅读全文
0 0
- Leetcode-Course Schedule && Course Schedule II
- leetcode-Course Schedule
- LeetCode 207 - Course Schedule
- [LeetCode] Course Schedule
- LeetCode Course Schedule
- [leetcode] Course Schedule
- Leetcode Course Schedule
- [leetcode]Course Schedule
- leetcode:Course Schedule
- [leetcode]Course Schedule II
- leetcode - Course Schedule II
- LeetCode Course Schedule II
- [leetcode] Course Schedule II
- [leetcode]Course Schedule
- leetcode:Course Schedule II
- [LeetCode] Course Schedule II
- Leetcode Course Schedule II
- leetcode 207: Course Schedule
- 二进制的运用 枚举
- effective C++ 09_绝不在构造和析构过程中调用virtual函数 读书笔记
- mybatis 用if标签判断字符串相等
- 设置 sudo 用户
- idea 使用 插件 技巧
- Course Schedule(leetcode)
- OS 图片压缩器 输出不同分辨率图片
- ActiveMq入门
- ssh登录图示
- IEEE754标准:二进位浮点数算术标准
- CronExpression表达式语法简介
- springboot thymeleaf + vue
- Android Studio 第三方库依赖集锦
- Mysql中的collation stage1-9