Completed Graph1

TheMaze.java

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+// Time Complexity : O(m*n)
+// Space Complexity : O(m*n))
+// Did this code successfully run on Leetcode : Yes
+// Any problem you faced while coding this : No
+
+
+// Your code here along with comments explaining your approach
+// We traverse all 4 directions from a point and add the stop points to a queue
+// Pop from the queue and mark as visited and repeat to find further stop points
+// If we stop at the destination return true else false
+
+import java.util.Queue;
+
+class Solution {
+    int[][] dirs;
+    int m,n;
+
+    public boolean hasPathDFS(int[][] maze, int[] start, int[] destination) {
+        this.dirs = new int[][]{{0,1},{0,-1},{1,0},{-1,0}};
+        m = maze.length;
+        n = maze[0].length;
+        return dfs(maze, start, destination);
+    }
+
+    private boolean dfs(int[][] maze, int[] start, int[] destination){
+        if(start[0] == destination[0] && start[1] == destination[1]) return true;
+
+        maze[start[0]][start[1]] = 2;
+        for(int[] dir:dirs){
+            int r = start[0];
+            int c = start[1];
+
+            while(r>=0 && r<m && c>=0 && c<n && maze[r][c] != 1){
+                r += dir[0];
+                c += dir[1];
+            }
+
+            r -= dir[0];
+            c -= dir[1];
+
+            if(maze[r][c] != 2){
+                if(dfs(maze, new int[]{r,c}, destination)) return true;
+            }
+        }
+
+        return false;
+    }
+
+
+    public boolean hasPathBFS(int[][] maze, int[] start, int[] destination) {
+
+        this.dirs = new int[][]{{0,1},{0,-1},{1,0},{-1,0}};
+        m = maze.length;
+        n = maze[0].length;
+
+        Queue<int[]> q = new LinkedList<>();
+        q.offer(start);
+        maze[start[0]][start[1]] = 2;
+
+        while(!q.isEmpty()){
+            int[] curr = q.poll();
+            if(curr[0] == destination[0] && curr[1] == destination[1]) return true;
+
+            for(int[] dir:dirs){
+                int r = curr[0];
+                int c = curr[1];
+
+                while(r>=0 && r<m && c>=0 && 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] != 2){
+                    q.offer(new int[]{r,c});
+                    maze[r][c] = 2;
+                }
+            }   
+        }
+
+        return false;
+    }
+}

TownJudge.java

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+// Time Complexity : O(V+E)
+// Space Complexity : O(V)
+// Did this code successfully run on Leetcode : Yes
+// Any problem you faced while coding this : No
+
+
+// Your code here along with comments explaining your approach
+// Count the number of incoming and outgoing edges for each person
+// for town judge, total of n-1 incoming edges and 0 outgoing edges
+// indegree should be n-1 
+
+class Solution {
+    public int findJudge(int n, int[][] trust) {
+
+        int[] indegrees = new int[n+1];
+        for(int[] edge:trust){ //O(E)
+            indegrees[edge[0]]--;
+            indegrees[edge[1]]++;
+        }
+
+        for(int i=1;i<indegrees.length;i++) //O(V)
+            if(indegrees[i]==n-1) return i;
+
+        return -1;
+    }
+}