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Author: rahul003t

1129-shortest-path-with-alternating-colors/1129-shortest-path-with-alternating-colors.java

@@ -0,0 +1,54 @@
+class Solution {
+    public int[] shortestAlternatingPaths(int n, int[][] redEdges, int[][] blueEdges) {
+        HashMap<Integer,Set<Pair<Integer,Integer>>> graph = new HashMap<>();// Here use set instead of array list is to prevent duplicate edges in same label
+        Queue<Pair<Integer,Integer>> queue  = new LinkedList<>();
+        Set<Pair<Integer,Integer>> visited = new HashSet<>();
+        int[] res = new int[n];
+        Arrays.fill(res,-1);
+        res[0] = 0;
+
+        for(int i=0;i<n;i++)
+        {
+            graph.put(i,new HashSet<>());
+        }
+
+        for(int[] redEdge:redEdges)
+        {
+            graph.get(redEdge[0]).add(new Pair<>(redEdge[1],1));
+        }
+        for(int[] blueEdge:blueEdges)
+        {
+            graph.get(blueEdge[0]).add(new Pair<>(blueEdge[1],2));
+        }
+
+        int dis = 0;
+        queue.add(new Pair<>(0,-1));
+        while(!queue.isEmpty())        
+        {
+            int size = queue.size();
+            for(int i=0;i<size;i++)
+            {
+                Pair<Integer,Integer> curPair = queue.poll();
+                int curNode = curPair.getKey();
+                int curLabel = curPair.getValue();
+                Set<Pair<Integer,Integer>> setPair = graph.get(curNode);
+                for(Pair<Integer,Integer> adjPair:setPair)
+                {
+                    int adjNode = adjPair.getKey();
+                    int adjLabel = adjPair.getValue();
+
+                    if(visited.contains(adjPair)||curLabel==adjLabel)
+                        continue;
+                    
+                    if(res[adjNode]==-1)
+                        res[adjNode] = dis+1;
+                    visited.add(adjPair);
+                    queue.add(adjPair);
+                }
+            }
+            dis++;
+        }
+
+        return res;
+    }
+}