Fast and precise algorithms, with tests

vpn_manager/cidr4_merge/precise.py

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+from .util import mask, get_data, cidr4_to_node, make_cidr4
+
+
+def f(x, y):
+    t = x
+    b = y
+    if x[1]>y[1]:
+        t = y
+        b = x
+    ip1, l1, a1 = t
+    ip2, l2, a2 = b
+    if ip1 & mask[l1] == ip2 & mask[l1]:
+        return (0, t)
+    t1 = t2 = 0
+    while not l1==l2:
+        t2 += 2**(32-l2)
+        l2 -= 1
+        ip2 = ip2 & mask[l2]
+    while not ip1 & mask[l1-1] == ip2 & mask[l2-1]:
+        t1 += 2**(32-l1)
+        l1 -= 1
+        ip1 = ip1 & mask[l1]
+        t2 += 2**(32-l2)
+        l2 -= 1
+        ip2 = ip2 & mask[l2]
+    r = (ip1 & mask[l1-1], l1-1, a1+a2+t1+t2)
+    return (t1+t2, r)
+    
+
+def solution(cidrs, M):
+    cidrs = sorted((ip, l, 0) for ip, l in cidrs)
+    while len(cidrs)>M:
+        t = (None, float('+inf'), None)
+        for i, (x, y) in enumerate(zip(cidrs, cidrs[1:])):
+            m, r = f(x, y)
+            if m<t[1]:
+                t = (i, m, r)
+            if m==0:
+                break
+        cidrs[t[0]] = t[2]
+        del cidrs[t[0]+1]
+    s = sum(x[2] for x in cidrs)
+    cidrs = [x[:2] for x in cidrs]
+    return cidrs, s
+
+
+def main():
+    M = 20
+    a = get_data()
+    b = list(map(cidr4_to_node, a))
+    cidrs, s = solution(b, M)
+    cidrs = sorted([make_cidr4(*x) for x in cidrs])
+    print(cidrs, s, sep='\n')
+    
+    
+
+if __name__=='__main__':
+    import cProfile
+    main()