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authorHaidong Ji2020-05-10 16:18:46 -0500
committerHaidong Ji2020-05-10 16:18:46 -0500
commitbc5a6815181068e76316aa4a611647124d18ba48 (patch)
treeaab5f2386523dfb064a51a689310a183f8286016 /src
Reachability done. I found it much easier to work with Java than Python. I tried to start with Python but found it difficult to get started.
Diffstat (limited to 'src')
-rw-r--r--src/main/Reachability.java47
-rw-r--r--src/test/ReachabilityTest.java38
2 files changed, 85 insertions, 0 deletions
diff --git a/src/main/Reachability.java b/src/main/Reachability.java
new file mode 100644
index 0000000..8d6ab78
--- /dev/null
+++ b/src/main/Reachability.java
@@ -0,0 +1,47 @@
+import java.util.ArrayList;
+import java.util.Scanner;
+
+public class Reachability {
+
+ static int reach(ArrayList<ArrayList<Integer>> adj, int x, int y) {
+ ArrayList<Integer> visited = new ArrayList<>();
+ if (x == y)
+ return 1;
+ explore(adj, visited, x, y);
+ if (visited.contains(y))
+ return 1;
+ return 0;
+ }
+
+ private static void explore(ArrayList<ArrayList<Integer>> adj, ArrayList<Integer> visited, int x, int y) {
+ visited.add(x);
+ if (x == y)
+ return;
+ for (int n : adj.get(x)) {
+ if (!visited.contains(n))
+ explore(adj, visited, n, y);
+ }
+ }
+
+
+ public static void main(String[] args) {
+ Scanner scanner = new Scanner(System.in);
+ int n = scanner.nextInt();
+ int m = scanner.nextInt();
+ ArrayList<ArrayList<Integer>> adj = new ArrayList<ArrayList<Integer>>();
+ for (int i = 0; i < n; i++) {
+ adj.add(new ArrayList<Integer>());
+ }
+ for (int i = 0; i < m; i++) {
+ int x, y;
+ x = scanner.nextInt();
+ y = scanner.nextInt();
+ adj.get(x - 1).add(y - 1);
+ adj.get(y - 1).add(x - 1);
+ }
+ int x = scanner.nextInt() - 1;
+ int y = scanner.nextInt() - 1;
+ System.out.println(reach(adj, x, y));
+ }
+}
+
diff --git a/src/test/ReachabilityTest.java b/src/test/ReachabilityTest.java
new file mode 100644
index 0000000..67b29b0
--- /dev/null
+++ b/src/test/ReachabilityTest.java
@@ -0,0 +1,38 @@
+import org.junit.jupiter.api.Test;
+
+import java.util.ArrayList;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class ReachabilityTest {
+
+ @Test
+ void test() {
+ ArrayList<ArrayList<Integer>> adj = new ArrayList<>();
+ for (int i = 0; i < 4; i++) {
+ adj.add(new ArrayList<>());
+ }
+
+ adj.get(0).add(1);
+ adj.get(2).add(1);
+ adj.get(3).add(2);
+ adj.get(0).add(3);
+
+ assertEquals(1, Reachability.reach(adj, 0, 3));
+ }
+
+ @Test
+ void test1() {
+ ArrayList<ArrayList<Integer>> adj = new ArrayList<>();
+ for (int i = 0; i < 4; i++) {
+ adj.add(new ArrayList<>());
+ }
+
+ adj.get(0).add(1);
+
+ adj.get(2).add(1);
+
+ assertEquals(0, Reachability.reach(adj, 0, 3));
+ }
+
+} \ No newline at end of file