updated journey-to-the-moon

Author: eloyekunle

hackerrank/graphs/journey-to-the-moon-2.py

@@ -0,0 +1,55 @@
+import sys
+from collections import Counter
+
+sys.setrecursionlimit(15000)
+
+def dfs(g, u, discovered, c):
+ for v in g[u]:
+ if v not in discovered:
+ discovered[v] = c
+ dfs(g, v, discovered, c)
+
+def journeyToMoon(n, astronaut):
+ g = {}
+ for i in range(n):
+ g[i] = set()
+
+ for a, b in astronaut:
+ g[a].add(b)
+ g[b].add(a)
+
+ forest = {}
+ component = 0
+ for v in range(n):
+ if v not in forest:
+ forest[v] = component
+ dfs(g, v, forest, component)
+ component += 1
+
+ vs = Counter(forest.values()).values()
+
+ c_sum = 0
+ result = 0
+ for s in vs:
+ result += c_sum * s
+ c_sum += s
+
+ return result
+
+if __name__ == '__main__':
+ f = open('/home/elijah/Downloads/input13.txt')
+
+ np = f.readline().split()
+
+ n = int(np[0])
+
+ p = int(np[1])
+
+ astronaut = []
+
+ for _ in range(p):
+ astronaut.append(list(map(int, f.readline().rstrip().split())))
+
+ result = journeyToMoon(n, astronaut)
+
+ print(result)

hackerrank/graphs/journey-to-the-moon.py

@@ -1,47 +1,88 @@
-import math
 import os
-import random
-import re
-import sys
-from collections import Counter
 
-def dfs(g, u, discovered, c):
- for v in g[u]:
- if v not in discovered:
- discovered[v] = c
- dfs(g, v, discovered, c)
+class Partition:
+ class Position:
+ __slots__ = '_container', '_element', '_size', '_parent'
 
+ def __init__(self, container, e):
+ self._container = container # reference to Partition instance
+ self._element = e
+ self._size = 1
+ self._parent = self # convention for a group leader
+
+ def element(self):
+ return self._element
+
+ def __len__(self):
+ return self._size
+
+ def __lt__(self, other):
+ return len(self) < len(other)
+
+ def __init__(self):
+ self._data = {}
+
+ def __len__(self):
+ return len(self._data)
+
+ def _validate(self, p):
+ if not isinstance(p, self.Position):
+ raise TypeError('p must be proper Position type')
+ if p._container is not self:
+ raise ValueError('p does not belong to this container')
+
+ def make_group(self, e):
+ position = self.Position(self, e)
+ self._data[e] = position
+ return position
+
+ def find(self, p):
+ self._validate(p)
+ if p._parent != p:
+ p._parent = self.find(p._parent) # overwrite p._parent after recursion
+ return p._parent
+
+ def positions(self):
+ return self._data.values()
+
+ def union(self, p, q):
+ a = self.find(p)
+ b = self.find(q)
+ if a is not b: # only merge if different groups
+ if a > b:
+ b._parent = a
+ a._size += b._size
+ if b.element() in self._data:
+ del self._data[b.element()]
+ else:
+ a._parent = b
+ b._size += a._size
+ if a.element() in self._data:
+ del self._data[a.element()]
+
+# Complete the journeyToMoon function below.
 def journeyToMoon(n, astronaut):
- g = {}
+ forest = Partition()
+ p = {}
  for i in range(n):
- g[i] = set()
+ p[i] = forest.make_group(i)
 
- for a, b in astronaut:
- g[a].add(b)
- g[b].add(a)
+ for a in astronaut:
+ forest.union(forest.find(p[a[0]]), forest.find(p[a[1]]))
 
- forest = {}
- component = 0
- for v in range(n):
- if v not in forest:
- forest[v] = component
- dfs(g, v, forest, component)
- component += 1
-
- vs = Counter(forest.values()).values()
+ vs = [len(x) for x in forest.positions()]
 
  c_sum = 0
  result = 0
  for s in vs:
- result += c_sum * s
+ result += c_sum*s
  c_sum += s
-
  return result
 
 if __name__ == '__main__':
- f = open('/home/elijah/Downloads/input13.txt')
+ fptr = open(os.environ['OUTPUT_PATH'], 'w')
 
- np = f.readline().split()
+ np = input().split()
 
  n = int(np[0])
 
@@ -50,8 +91,10 @@ def journeyToMoon(n, astronaut):
  astronaut = []
 
  for _ in range(p):
- astronaut.append(list(map(int, f.readline().rstrip().split())))
+ astronaut.append(list(map(int, input().rstrip().split())))
 
  result = journeyToMoon(n, astronaut)
 
- print(result)
+ fptr.write(str(result) + '\n')
+
+ fptr.close()