Adding solutions for Assignment 5

Author: tachyonlabs

README.md

@@ -178,3 +178,18 @@ When I went to take the HackerRank "CodePath Interview Prep - Unit 4 Test", once
 And here's a GIF of my InterviewBit Graphs topic page:
 
 * [GIF of my InterviewBit Graphs topic page](https://github.com/tachyonlabs/CodePath-Alumni-Professional-Interview-Prep-Course/blob/master/interviewbit-graphs-topics.gif)
+
+## Assignment 5
+
+I completed four more InterviewBit Graphs problems:
+
+* Possibility Of Finishing All Courses Given Pre Requisites
+* Word Search Board
+* Knight on Chess Board
+* Clone Graph
+
+And here's a GIF of my updated InterviewBit Graphs topic page:
+
+* GIF of my InterviewBit Graphs topic page
+
+I took the "CodePath Interview Prep - Unit 5" test on January 28, so you should have received it.

interviewbit-graphs-clone-graph.py

@@ -0,0 +1,39 @@
+# Definition for a undirected graph node
+# class UndirectedGraphNode:
+# def __init__(self, x):
+# self.label = x
+# self.neighbors = []
+from collections import deque
+
+
+class Solution:
+ # @param node, a undirected graph node
+ # @return a undirected graph node
+ def cloneGraph(self, node):
+ cloned_nodes = {}
+ checked = {}
+ cloned_start_node = None
+ queue = deque([node])
+ # first a BFS to clone all the nodes but with empty neighbors lists
+ while queue:
+ current = queue.popleft()
+ cloned_nodes[current.label] = UndirectedGraphNode(current.label)
+ if not cloned_start_node:
+ cloned_start_node = cloned_nodes[current.label]
+ checked[current] = 1
+ for neighbor in current.neighbors:
+ if neighbor not in checked and neighbor not in queue:
+ queue.append(neighbor)
+
+ # then another round to fill in the neighbors lists
+ checked = {}
+ queue = deque([node])
+ while queue:
+ current = queue.popleft()
+ checked[current] = 1
+ for neighbor in current.neighbors:
+ cloned_nodes[current.label].neighbors.append(cloned_nodes[neighbor.label])
+ if neighbor not in checked and neighbor not in queue:
+ queue.append(neighbor)
+
+ return cloned_start_node

interviewbit-graphs-knight-on-chess-board.py

@@ -0,0 +1,30 @@
+from collections import deque
+
+class Solution:
+ # @param A : integer
+ # @param B : integer
+ # @param C : integer
+ # @param D : integer
+ # @param E : integer
+ # @param F : integer
+ # @return an integer
+ def knight(self, A, B, C, D, E, F):
+ directions = [(-2, 1), (-1, 2), (1, 2), (2, 1), (2, -1), (1, -2), (-1, -2), (-2, -1)]
+ dest = [F, E]
+ source = [D, C]
+ rows = B
+ cols = A
+ queue = deque([source + [0]])
+ dont_check_again = [[False for c in range(cols + 1)] for r in range(rows + 1)]
+ dont_check_again[D][C] = True
+ while queue:
+ row, col, steps = queue.popleft()
+ if [row, col] == dest:
+ return steps
+ for y, x in directions:
+ new_y, new_x = row + y, col + x
+ if new_y >= 1 and new_y <= rows and new_x >= 1 and new_x <= cols and not dont_check_again[new_y][new_x]:
+ queue.append([new_y, new_x, steps + 1])
+ dont_check_again[new_y][new_x] = True
+
+ return -1

interviewbit-graphs-possibility-of-finishing-all-courses-given-prerequisites.py

@@ -0,0 +1,32 @@
+class Solution:
+ # @param A : integer
+ # @param B : list of integers
+ # @param C : list of integers
+ # @return an integer
+ def is_cycle(self, num):
+ if num in self.black:
+ return False
+ if num in self.gray:
+ return True
+ del self.white[num]
+ self.gray[num] = 1
+ return any([self.is_cycle(n) for n in self.course_list[num]])
+
+ def solve(self, A, B, C):
+ self.white = {i: 1 for i in range(1, A + 1)}
+ self.gray = {}
+ self.black = {}
+ self.course_list = [[] for i in range(A + 1)]
+ for i in range(len(B)):
+ self.course_list[C[i]].append(B[i])
+
+ for i in range(1, A + 1):
+ if self.is_cycle(i):
+ return 0
+ else:
+ keys = self.gray.keys()
+ for key in keys:
+ del self.gray[key]
+ self.black[key] = 1
+
+ return 1

interviewbit-graphs-topics-2.gif

@@ -0,0 +1,28 @@
+class Solution:
+ # @param A : list of strings
+ # @param B : string
+ # @return an integer
+ def __init__(self):
+ self.directions = [(0, 1), (1, 0), (0, -1), (-1, 0)]
+ self.bad = {}
+
+ def word_search(self, r, c, idx):
+ if idx == len(self.word):
+ return True
+ if (r, c, idx) in self.bad or r < 0 or c < 0 or r >= len(self.A) or c >= len(self.A[r]):
+ return False
+ if self.A[r][c] != self.word[idx]:
+ self.bad[(r, c, idx)] = 1
+ return False
+ return any(self.word_search(r + y, c + x, idx + 1) for y, x in self.directions)
+
+ def exist(self, A, B):
+ # InterviewBit is putting a space on the end of at least one test case :-(!!!
+ self.word = B.strip()
+ self.A = A
+ for row in range(len(A)):
+ for col in range(len(A[row])):
+ if A[row][col] == B[0] and self.word_search(row, col, 0):
+ return 1
+
+ return 0