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Task/Find-the-missing-permutation/Nim/find-the-missing-permutation.nim

@@ -0,0 +1,19 @@
+import strutils
+
+proc missingPermutation(arr): string =
+  result = ""
+  if arr.len == 0: return
+  if arr.len == 1: return arr[0][1] & arr[0][0]
+
+  for pos in 0 .. <arr[0].len:
+    var s: set[char] = {}
+    for permutation in arr:
+      let c = permutation[pos]
+      if c in s: s.excl c
+      else:      s.incl c
+    for c in s: result.add c
+
+const given = """ABCD CABD ACDB DACB BCDA ACBD ADCB CDAB DABC BCAD CADB CDBA
+  CBAD ABDC ADBC BDCA DCBA BACD BADC BDAC CBDA DBCA DCAB""".split()
+
+echo missingPermutation(given)