Solution to today's problem

Author: spannm

src/main/java/io/github/spannm/leetcode/lc2/lc2100/Problem2192.java

@@ -3,47 +3,38 @@
 import io.github.spannm.leetcode.LeetcodeProblem;
 
 import java.util.*;
+import java.util.stream.IntStream;
 
 /**
  * 2192. All Ancestors of a Node in a Directed Acyclic Graph.
  */
 class Problem2192 extends LeetcodeProblem {
 
-    private int                 n;
-    private List<Integer>[]     g;
-    private List<List<Integer>> ans;
-
-    public List<List<Integer>> getAncestors(int _n, int[][] _edges) {
+    List<List<Integer>> getAncestors(int _n, int[][] _edges) {
         @SuppressWarnings("unchecked")
-        List<Integer>[] lists = new List[_n];
-        g = lists;
-        n = _n;
-        Arrays.setAll(g, i -> new ArrayList<>());
-        for (var e : _edges) {
-            g[e[0]].add(e[1]);
-        }
-        ans = new ArrayList<>();
-        for (int i = 0; i < _n; i++) {
-            ans.add(new ArrayList<>());
-        }
-        for (int i = 0; i < _n; i++) {
-            bfs(i);
+        List<Integer>[] graph = new List[_n];
+        Arrays.setAll(graph, i -> new ArrayList<>());
+        for (int[] e : _edges) {
+            graph[e[0]].add(e[1]);
         }
-        return ans;
+        List<List<Integer>> result = new ArrayList<>();
+        IntStream.range(0, _n).forEach(i -> result.add(new ArrayList<>()));
+        IntStream.range(0, _n).forEach(i -> bfs(i, graph, result));
+        return result;
     }
 
-    private void bfs(int s) {
+    static void bfs(int _s, List<Integer>[] _graph, List<List<Integer>> _result) {
         Deque<Integer> q = new ArrayDeque<>();
-        q.offer(s);
-        boolean[] vis = new boolean[n];
-        vis[s] = true;
+        q.offer(_s);
+        boolean[] visited = new boolean[_result.size()];
+        visited[_s] = true;
         while (!q.isEmpty()) {
             int i = q.poll();
-            for (int j : g[i]) {
-                if (!vis[j]) {
-                    vis[j] = true;
+            for (int j : _graph[i]) {
+                if (!visited[j]) {
+                    visited[j] = true;
                     q.offer(j);
-                    ans.get(j).add(s);
+                    _result.get(j).add(_s);
                 }
             }
         }

src/test/java/io/github/spannm/leetcode/lc2/lc2100/Problem2192Test.java

@@ -0,0 +1,21 @@
+package io.github.spannm.leetcode.lc2.lc2100;
+
+import io.github.spannm.leetcode.LeetcodeBaseTest;
+import java.util.List;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.converter.ConvertWith;
+import org.junit.jupiter.params.provider.CsvSource;
+
+class Problem2192Test extends LeetcodeBaseTest {
+    @ParameterizedTest(name = "[{index}] {0}; {1} --> {2}")
+    @CsvSource(delimiter = ';', value = {
+        "8; [0,3],[0,4],[1,3],[2,4],[2,7],[3,5],[3,6],[3,7],[4,6]; [],[],[],[0,1],[0,2],[0,1,3],[0,1,2,3,4],[0,1,2,3]",
+        "5; [0,1],[0,2],[0,3],[0,4],[1,2],[1,3],[1,4],[2,3],[2,4],[3,4]; [],[0],[0,1],[0,1,2],[0,1,2,3]"
+    })
+    void test(
+        int _n,
+        @ConvertWith(CsvToIntMatrix.class) int[][] _edges,
+        @ConvertWith(CsvToListOfIntegerLists.class) List<List<Integer>> _expectedResult) {
+        assertEquals(_expectedResult, new Problem2192().getAncestors(_n, _edges));
+    }
+}