Graph problems 1-3

khudiakov/A1_components.py

@@ -0,0 +1,75 @@
+
+import sys
+import threading
+
+
+
+def main():
+
+    # read number of vertices
+    f = open('components.in')
+    first_string = f.readline().strip().split(' ')
+    n = int(first_string[0])
+
+    #read edges list
+    next_string = ' '
+    edges_list = []
+    inner_list = []
+    while next_string != ['']:
+        next_string = f.readline().strip().split(' ')
+        if next_string != ['']:
+            inner_list.append(int(next_string[0])-1)
+            inner_list.append(int(next_string[1])-1)
+            edges_list.append(inner_list)
+        inner_list = []
+    f.close()
+
+    # make full edges list with reverse edges
+    rev_edges_list = []
+    for i in edges_list:
+        a = i[::-1]
+        rev_edges_list.append(a)
+    full_edges_list = edges_list + rev_edges_list
+
+    #convert edges list to adjacency list
+    adjacency_list = []
+
+    for i in range(n):
+        adjacency_list.append([])
+
+    for i in full_edges_list:
+        a = (i[0])
+        adjacency_list[a].append(i[1])
+
+    #dfs
+    visited = [False] * n
+    comp_number = 0
+    components_list = [-1] * n
+
+    def dfs(v):
+        components_list[v] = comp_number
+        visited[v] = True
+        for w in adjacency_list[v]:
+            if not visited[w]:
+                dfs(w)
+
+    #counting components
+    for v in range(n):
+        if not visited[v]:
+            dfs(v)
+            comp_number += 1
+
+
+    #write to file
+
+    ans = open('components.out', 'w')
+    ans.write(str(comp_number) + '\n')
+    for w in components_list:
+        ans.write(str(int(w) + 1) + ' ')
+    ans.close()
+
+
+threading.stack_size(2 ** 26) # 64 MB stack size
+sys.setrecursionlimit(1000000000) # recursion depth
+thread = threading.Thread(target=main)
+thread.start()

khudiakov/A2_Shortest.py

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+
+import sys
+import threading
+
+def main():
+
+   # read number of vertices
+   f = open('pathbge1.in')
+   v, e = (int(i) for i in f.readline().strip().split())
+
+
+   #adjacency list
+   adjacency_list=[[] for i in range(v)]
+   for edge in f:
+       x, y = ((int(i) - 1) for i in edge.strip().split())
+       adjacency_list[x].append(y)
+       adjacency_list[y].append(x)
+
+   #bfs
+   visited = [False] * v
+   distance = [-1 for i in range(v)]
+
+   def bfs(start, adjacency_list):
+       queue = [start]
+       visited[start] = True
+       distance[start] = 0 # distance from start vertex to current one
+       while len(queue) > 0:
+
+           x = queue.pop(0)
+
+           for i in adjacency_list[x]:
+                   if visited[i] == False:
+                       queue.append(i)
+                       visited[i] = True
+                       if distance[i] == -1:
+                          distance[i] = distance[x] + 1
+       return distance
+
+   #write to file
+
+   ans = open('pathbge1.out', 'w')
+   for w in bfs(0, adjacency_list):
+        ans.write(str(int(w)) + ' ')
+   ans.close()
+
+
+threading.stack_size(2 ** 26) # 64 MB stack size
+sys.setrecursionlimit(1000000000) # recursion depth
+thread = threading.Thread(target=main)
+thread.start()

khudiakov/A3_Shortest_with_weight.py

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+
+import sys
+sys.setrecursionlimit(1000000000)
+
+#read number of vertices, star and stop points from file
+file = open('pathmgep.in', 'r')
+
+n, s, f = [int(i) for i in file.readline().split()]
+s-= 1
+f-= 1
+
+#read weight matrix
+path = []
+for string in file.read().splitlines():
+    weight = [int(i) for i in string.split()]
+    path.append(weight)
+file.close()
+
+#mark nonexistent paths
+for i in range(n):
+    for j in range(n):
+        if path[i][j] == -1:
+            path[i][j] = '-1'
+
+#may be slow but..
+def FloydWarshall(path):
+    for k in range(n):
+        for i in range(n):
+            for j in range(n):
+                if path[i][j] != '-1'and path[i][k] != '-1'and path[k][j] != '-1':
+                      path[i][j] = min(path[i][j], (path[i][k] + path[k][j]))
+                elif path[i][j] != '-1'and (path[i][k] == '-1'or path[k][j] == '-1'):
+                    path[i][j] = path[i][j]
+                elif path[i][j] == '-1'and path[i][k] != '-1'and path[k][j] != '-1':
+                    path[i][j] = path[i][k] + path[k][j]
+                else:
+                    path[i][j] = '-1'
+    return path
+
+FloydWarshall(path)
+
+
+ans = open('pathmgep.out', 'w')
+ans.write(str(path[s][f]))
+ans.close()