add new solutions

solutions/2/q207/solution.go

@@ -0,0 +1,37 @@
+package q207
+
+func canFinish(numCourses int, prerequisites [][]int) bool {
+	nDeps := make([]int, numCourses)
+	revDeps := make([][]int, numCourses)
+
+	for i := range prerequisites {
+		course, prereq := prerequisites[i][0], prerequisites[i][1]
+		nDeps[course]++
+		revDeps[prereq] = append(revDeps[prereq], course)
+	}
+
+	queue := []int{}
+	for i := range numCourses {
+		if nDeps[i] == 0 && len(revDeps) > 0 {
+			queue = append(queue, i)
+		}
+	}
+	for ; len(queue) > 0; queue = queue[1:] {
+		course := queue[0]
+		for _, r := range revDeps[course] {
+			nDeps[r]--
+			if nDeps[r] == 0 {
+				queue = append(queue, r)
+			}
+		}
+	}
+
+	for _, n := range nDeps {
+		if n > 0 {
+			return false
+		}
+	}
+	return true
+}
+
+var _ = canFinish