basic enumeration of permutations

active_projects/eop/chapter2.py

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+from big_ol_pile_of_manim_imports import *
+
+def print_permutation(index_list):
+
+
+    n = max(max(index_list), len(index_list))
+    for i in range(0,n):
+        if index_list[i] > n - i:
+            raise Exception("Impossible indices!")
+
+    #print "given index list:", index_list
+    perm_list = n * ["_"]
+    alphabet = ["A", "B", "C", "D", "E", "F",
+                "G", "H", "I", "J", "K", "L",
+                "M", "N", "O", "P", "Q", "R",
+                "S", "T", "U", "V", "W", "X",
+                "Y", "Z"]
+    free_indices = range(n)
+    free_indices_p1 = range(1,n + 1)
+    #print perm_list
+    for i in range(n):
+        findex = index_list[i] - 1
+        #print "place next letter at", findex + 1, "th free place"
+        tindex = free_indices[findex]
+        #print "so at position", tindex + 1
+        perm_list[tindex] = alphabet[i]
+        free_indices.remove(tindex)
+        free_indices_p1.remove(tindex + 1)
+        #print "remaining free places:", free_indices_p1
+        #print perm_list
+
+    return "".join(perm_list)
+
+
+
+
+
+N = 5
+
+index_list = []
+for i in range(1, N + 1):
+    index_list.append(i)
+    for j in range(1, N):
+        index_list.append(j)
+        for k in range(1, N - 1):
+            index_list.append(k)
+            for l in range(1, N - 2):
+                index_list.append(l)
+                for m in range(1, N - 3):
+                    index_list.append(m)
+                    print print_permutation(index_list)
+                    index_list.pop()
+                index_list.pop()
+            index_list.pop()
+        index_list.pop()
+    index_list.pop()
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