190523

Author: aluferraz

src/Main.java

@@ -19,6 +19,7 @@
 import leetcode.editor.en.Q639.DecodeWaysIi;
 import leetcode.editor.en.Q649.Dota2Senate;
 import leetcode.editor.en.Q651.FourKeysKeyboard;
+import leetcode.editor.en.Q785.IsGraphBipartite;
 import leetcode.editor.en.Q91.DecodeWays;
 import org.json.JSONArray;
 import org.json.JSONTokener;
@@ -34,7 +35,7 @@
 public class Main {
     public static void main(String[] args) throws IOException {
 
-        System.out.println(new DecodeWaysIi().numDecodings("********"));
+        System.out.println(new IsGraphBipartite().isBipartite(toIntMatrix("[[1,2,3],[0,2],[0,1,3],[0,2]]")));
 
     }
 

src/leetcode/editor/en/Q785/IsGraphBipartite.java

@@ -0,0 +1,72 @@
+package leetcode.editor.en.Q785;
+
+import java.util.*;
+
+import javafx.util.Pair;
+
+//leetcode submit region begin(Prohibit modification and deletion)
+class Solution {
+
+    private static final int GRAY = 0;
+    private static final int BLUE = 1;
+    private static final int GREEN = 2;
+
+    public boolean isBipartite(int[][] graph) {
+        HashMap<Integer, Integer> colors = new HashMap<>();
+        HashMap<Integer, HashSet<Integer>> adjList = makeAdjList(graph);
+        for (int i = 0; i < graph.length; i++) {
+            colors.put(i, GRAY);
+        }
+        for (int i = 0; i < graph.length; i++) {
+            if (colors.get(i) != GRAY) continue;
+            if (!checkBipartition(i, adjList, colors)) return false;
+        }
+        return true;
+    }
+
+    private boolean checkBipartition(int root,
+                                     HashMap<Integer, HashSet<Integer>> adjList,
+                                     HashMap<Integer, Integer> colors) {
+        Queue<int[]> queue = new LinkedList<>();
+        queue.add(new int[]{root, BLUE});
+        HashSet<Integer> visited = new HashSet<>();
+        while (!queue.isEmpty()) {
+            int size = queue.size();
+            for (int i = 0; i < size; i++) {
+                int[] shouldBeInfo = queue.poll();
+                int node = shouldBeInfo[0];
+                int color = shouldBeInfo[1];
+                colors.put(node, color);
+                visited.add(node);
+                if (!adjList.containsKey(node)) continue;
+                HashSet<Integer> connected = adjList.get(node);
+                int newColor = color == BLUE ? GREEN : BLUE;
+                for (int next : connected) {
+                    if (colors.get(next) != GRAY && colors.get(next) != newColor) {
+                        return false;
+                    }
+                    if (!visited.contains(next)) queue.add(new int[]{next, newColor});
+                }
+            }
+        }
+        return true;
+
+    }
+
+    private HashMap<Integer, HashSet<Integer>> makeAdjList(int[][] graph) {
+        HashMap<Integer, HashSet<Integer>> adjList = new HashMap<>();
+        for (int i = 0; i < graph.length; i++) {
+            int from = i;
+            for (int to : graph[i]) {
+                adjList.computeIfAbsent(from, (v) -> new HashSet<>()).add(to);
+                adjList.computeIfAbsent(to, (v) -> new HashSet<>()).add(from);
+            }
+        }
+        return adjList;
+    }
+}
+//leetcode submit region end(Prohibit modification and deletion)
+
+
+public class IsGraphBipartite extends Solution {
+}