day 25 solution

day25/sample2.in

@@ -0,0 +1,13 @@
+jqt: rhn xhk nvd
+rsh: frs pzl lsr
+xhk: hfx
+cmg: qnr nvd lhk bvb
+rhn: xhk bvb hfx
+bvb: xhk hfx
+pzl: lsr hfx nvd
+qnr: nvd
+ntq: jqt hfx bvb xhk
+nvd: lhk
+lsr: lhk
+rzs: qnr cmg lsr rsh
+frs: qnr lhk lsr

day25/sol.py

@@ -0,0 +1,124 @@
+import sys
+import random
+from pprint import pprint
+
+def main():
+    G = {}
+    for line in sys.stdin:
+        n, to = line.split(": ")
+        to = to.split()
+        G[n] = to
+
+    pprint(G)
+
+    # mke connections symmetric
+    for n in list(G):
+        for t in G[n]:
+            G.setdefault(t,[])
+            if n not in G[t]:
+                G[t].append(n)
+
+    G = {n:tuple(t) for n,t in G.items()}
+    pprint(G)
+
+    print([len(g) for g in connected_components(G, set())])
+    def key(e):
+        v,t = e
+        return sort2(len(G[v]),len(G[t]))
+    E = sorted(set(sort2(v,t) for v in G for t in G[v]), key=key)
+
+    print(connected_components(G, {sort2('hfx','pzl'), sort2('bvb','cmg'), sort2('jqt','nvd')}))
+
+    num = 100
+    while num > 3:
+        num, fwd = karger_stein(G, E)
+
+    P = {}
+    for v,t in fwd.items():
+        P.setdefault(v,[])
+        P.setdefault(t,[])
+        P[v].append(t)
+        P[t].append(v)
+    cc = connected_components(P, set())
+    print([len(x) for x in cc])
+    print(len(cc[0]) * len(cc[1]))
+
+
+
+def karger_stein(G,E):
+    num = len(G)
+    fwd = {}
+    while num > 2:
+        # choose a random e
+        v,t = random.choice(E)
+        # contract the edge
+        fwd[v] = t
+        F = []
+        for v,t in E:
+            v = fwd.get(v,v)
+            t = fwd.get(t,t)
+            if v != t:
+                F.append((v,t))
+        E = F
+        num -= 1
+    print(len(E), E)
+    return len(E), fwd
+
+def brute_force(x):
+    print([len(g) for g in connected_components(G, set())])
+    def key(e):
+        v,t = e
+        return sort2(len(G[v]),len(G[t]))
+    E = sorted(set(sort2(v,t) for v in G for t in G[v]), key=key)
+    E = [(v,t) for v,t in E if len(G[t]) <= 3 and len(G[v]) <= 3]
+
+    print(connected_components(G, {sort2('hfx','pzl'), sort2('bvb','cmg'), sort2('jqt','nvd')}))
+
+    #assert set(E) > {sort2('hfx','pzl'), sort2('bvb','cmg'), sort2('jqt','nvd')}
+
+    for i,e1 in enumerate(E):
+        print("#", i, e1)
+        for j,e2 in enumerate(E[i+1:], start=i+1):
+            for e3 in E[j+1:]:
+                cc = connected_components(G, {e1,e2,e3})
+                if len(cc) > 1 and not any(len(g) == 1 for g in cc):
+                    #print(cc)
+                    print(e1,e2,e3)
+                    print([len(x) for x in cc])
+                    print(len(cc[0]) * len(cc[1]))
+
+
+def connected_components(G, nope):
+    V = [v for v in G]
+    mark = set()
+    cc = []
+    #print(nope)
+    while V:
+        node = V.pop()
+        if node in mark:
+            continue
+        group = []
+
+        def visit(node):
+            queue = [node]
+            while queue:
+                n = queue.pop()
+                if n in mark:
+                    continue
+                mark.add(n)
+                group.append(n)
+                if n in G:
+                    for t in G[n]:
+                        if t not in mark and sort2(n,t) not in nope:
+                            queue.append(t)
+        visit(node)
+
+        assert len(group) > 0
+        cc.append(group)
+    return cc
+
+def sort2(a,b):
+    return min(a,b), max(a,b)
+
+
+main()