leet code
3868 - Course Schedule II
khan topological sort
overall poor implementation
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77 | #include<algorithm>
#include<vector>
using namespace std;
class Solution {
public:
vector<int> findOrder(int numCourses, vector<vector<int>>& prerequisites) {
// construct graph
vector<vector<int>> graph;
vector<vector<int>> graphInv;
for(int i=0; i<numCourses; ++i)
{
graph.push_back(vector<int>{});
graphInv.push_back(vector<int>{});
}
for(int i=0; i<prerequisites.size(); ++i)
{
vector<int> curRelation = prerequisites[i];
graph[curRelation[1]].push_back(curRelation[0]);
graphInv[curRelation[0]].push_back(curRelation[1]);
}
queue<int> q;
vector<int> result;
// find the first nodes
for(int i=0; i<numCourses; ++i)
{
if(graphInv[i].size() == 0)
{
q.push(i);
}
}
// loop
while(!q.empty())
{
int curIdx = q.front();
q.pop();
int isVisited = false;
for(int i=0; i<result.size(); ++i)
{
if(result[i] == curIdx)
{
isVisited = true;
break;
}
}
if(graphInv[curIdx].size() == 0 && !isVisited) // indegree == 0
{
// break the connections
for(int i=0; i<graph[curIdx].size(); ++i)
{
int deletedIdx = graph[curIdx][i];
graphInv[deletedIdx].erase(remove(graphInv[deletedIdx].begin(), graphInv[deletedIdx].end(), curIdx), graphInv[deletedIdx].end());
q.push(deletedIdx);
}
graph[curIdx].clear();
// insert into result
result.push_back(curIdx);
}
}
if(result.size() == numCourses)
{
return result;
}else
{
return vector<int>{};
}
}
};
|