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207+Course Schedule.cpp
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207+Course Schedule.cpp
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class Solution {
public:
vector<int> findOrder(int numCourses, vector<vector<int>>& prerequisites) {
edges.resize(numCourses);
indeg.resize(numCourses);
for (const auto& info: prerequisites) {
edges[info[1]].push_back(info[0]); // 注意这里
++indeg[info[0]];
}
queue<int> q;
// 将所有入度为 0 的节点放入队列中
for (int i = 0; i < numCourses; ++i) {
if (indeg[i] == 0) q.push(i);
}
while (!q.empty()) {
// 从队首取出一个节点
int u = q.front(); q.pop();
// 放入答案中
result.push_back(u);
for (int v: edges[u]) {
--indeg[v];
// 如果相邻节点 v 的入度为 0,就可以选 v 对应的课程了
if (indeg[v] == 0) q.push(v);
}
}
if (result.size() != numCourses) return {};
return result;
}
private:
// 存储有向图
vector<vector<int>> edges;
// 存储每个节点的入度
vector<int> indeg;
// 存储答案
vector<int> result;
};
class Solution {
private:
// 存储有向图
vector<vector<int>> edges;
// 存储每个节点的出度 出度 出度 出度 出度 出度
vector<int> outdeg;
// 存储答案
vector<int> result;
public:
vector<int> findOrder(int numCourses, vector<vector<int>>& prerequisites) {
edges.resize(numCourses);
outdeg.resize(numCourses);
for (const auto& info: prerequisites) {
edges[info[0]].push_back(info[1]); //!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
++outdeg[info[1]]; //!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
}
queue<int> q;
// 将所有出度为 0 的节点放入队列中
for (int i = 0; i < numCourses; ++i) {
if (outdeg[i] == 0) q.push(i);
}
while (!q.empty()) {
// 从队首取出一个节点
int u = q.front(); q.pop();
// 放入答案中
result.push_back(u);
for (int v: edges[u]) {
--outdeg[v];
// 如果相邻节点 v 的入度为 0,就可以选 v 对应的课程了
if (outdeg[v] == 0) q.push(v);
}
}
if (result.size() != numCourses) return {};
reverse(result.begin(), result.end()); //!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
return result;
}
};