Add Q207

Author: theFool32

207_CourseSchedule/CourseShedule.cc

@@ -0,0 +1,39 @@
+class Solution {
+public:
+    bool canFinish(int numCourses, vector<pair<int, int>>& prerequisites) {
+        vector<vector<int>> inGraph(numCourses, vector<int>());
+        vector<vector<int>> outGraph(numCourses, vector<int>());
+        vector<bool> okCourse(numCourses, true);
+
+        for (auto&& prerequisite : prerequisites) {
+            outGraph[prerequisite.first].push_back(prerequisite.second);
+            inGraph[prerequisite.second].push_back(prerequisite.first);
+            okCourse[prerequisite.first] = false;
+            okCourse[prerequisite.second] = false;
+        }
+        while (true) {
+            bool changed = false;
+            for (int i = 0; i < numCourses; ++i) {
+                if (okCourse[i]) continue;
+
+                if (inGraph[i].empty()) {
+                    okCourse[i] = true;
+                    for (int j = 0; j < outGraph[i].size(); ++j) {
+                        changed = true;
+                        auto it = find(std::begin(inGraph[outGraph[i][j]]), std::end(inGraph[outGraph[i][j]]), i);
+                        if (it != std::end(inGraph[outGraph[i][j]])) {
+                            inGraph[outGraph[i][j]].erase(it);
+                        }
+                    }
+                }
+            }
+            if (!changed) {
+                break;
+            }
+        }
+        for (int i = 0; i < numCourses; ++i) {
+            if (!okCourse[i]) return false;
+        }
+        return true;
+    }
+};