Completed Graph-1

BallInMaze.java

@@ -0,0 +1,47 @@
+import java.util.LinkedList;
+import java.util.Queue;
+
+//Idea is to use bfs to traverse and mark the visited cells to avoid going through cycles
+//Time Complexity:O(m*n)
+//Space Complexity:O(m*n)
+public class BallInMaze {
+    int[][] dirs;
+    int m,n;
+    public boolean findBall(int[][] maze, int[] start, int[] destination) {
+        this.dirs = new int[][]{{-1,0},{1,0},{0,1},{0,-1}};
+        this.m = maze.length;
+        this.n = maze[0].length;
+
+        Queue<int[]> q = new LinkedList<>();
+        q.add(new int[]{start[0], start[1]});
+        maze[start[0]][start[1]] = -1;
+
+        while(!q.isEmpty())
+        {
+            int[] curr = q.poll();
+            for(int[] dir: dirs)
+            {
+                int r = dir[0] + curr[0];
+                int c = dir[1] + curr[1];
+
+                while(r>=0 && c>=0 && r<m && c<n && maze[r][c] != 1)
+                {
+                    r += dir[0];
+                    c += dir[1];
+                }
+
+                r -= dir[0];
+                c -= dir[1];
+
+                if(r == destination[0] && c == destination[1]) return true;
+                if(maze[r][c] != -1)
+                {
+                    q.add(new int[]{r,c});
+                    maze[r][c] = -1;
+                }
+            }
+        }
+        return false;
+
+    }
+}

FindJudge.java

@@ -0,0 +1,20 @@
+public class FindJudge {
+    //Idea is to use indegrees and out degrees array to find judge with no out degrees and all in degrees.
+    //Time Complexity: O(n)
+    //Space Complecitty:O(n)
+       public int findJudge(int n, int[][] trust) {
+        int[] indegrees = new int[n+1];
+        int[] outDegrees = new int[n+1];
+
+        for(int[] tr: trust){
+            outDegrees[tr[0]]++;
+            indegrees[tr[1]]++;
+        }
+
+        for(int i=1; i<=n; i++){
+            if(indegrees[i] == n-1 && outDegrees[i] == 0) return i;
+        }
+
+        return -1;
+    }
+}