Done Graph-1

find-the-town-judge.py

@@ -0,0 +1,18 @@
+''' 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
+
+'''
+
+class Solution:
+    def findJudge(self, n: int, trust: List[List[int]]) -> int:
+        indegree = [0] * (n+1)
+        for i,j in trust:
+            indegree[j] += 1
+            indegree[i] -= 1
+        for i in range(1,n+1):
+            if indegree[i] == n-1:
+                return i
+
+        return -1

the-maze.py

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+#--------Solution 1 : BFS---------------
+''' 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
+
+'''
+
+class Solution:
+    def hasPath(self, maze: List[List[int]], start: List[int], destination: List[int]) -> bool:
+        m, n = len(maze),len(maze[0])
+        dirs = [(0,1),(0,-1),(1,0),(-1,0)]
+        q = deque()
+        q.append((start[0],start[1]))
+        maze[start[0]][start[1]] = 2
+        while q:
+            i, j = q.pop()
+            for dir in dirs:
+                r = dir[0] + i
+                c = dir[1] + j
+
+                while 0<=r<m and 0<=c<n and maze[r][c] != 1:
+                    r = dir[0] + r
+                    c = dir[1] + c
+
+                #step back
+                r = -dir[0] + r
+                c = -dir[1] + c
+
+                if destination[0] == r and destination[1] == c:
+                    return True
+                if maze[r][c] != 2:
+                    maze[r][c] = 2
+                    q.append((r,c))
+
+        return False
+
+#--------Solution 2 : DFS---------------
+''' 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
+
+'''
+class Solution:
+    def hasPath(self, maze: List[List[int]], start: List[int], destination: List[int]) -> bool:
+        m, n = len(maze),len(maze[0])
+        dirs = [(0,1),(0,-1),(1,0),(-1,0)]
+        self.destination = destination
+
+        def dfs(i, j, maze):
+            if [i,j] == destination:
+                return True
+            maze[i][j] = 2
+
+            for dir in dirs:
+                r = dir[0] + i
+                c = dir[1] + j
+
+                while 0<=r<m and 0<=c<n and maze[r][c] != 1:
+                    r = dir[0] + r
+                    c = dir[1] + c
+
+                #step back
+                r = -dir[0] + r
+                c = -dir[1] + c
+
+                if maze[r][c] != 2:
+                    if dfs(r,c,maze):
+                        return True
+            return False
+
+        return dfs(start[0],start[1],maze)
+
+
+
+