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diff --git a/reference/C/CONTRIB/SNIP/perm_idx.c b/reference/C/CONTRIB/SNIP/perm_idx.c
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+/*
+** Determine the permutation index for a given permutation list.
+** Written by Thad Smith III, Boulder, CO  8/31/91
+** Hereby contributed to the Public Domain.
+**
+** The following function computes the ordinal of the given permutation,
+** which is index of the permutation in sorting order:
+**  1, 2, ..., n-1, n   is index 0
+**  1, 2, ..., n, n-1   is index 1
+**  ...
+**  n, n-1, ..., 2, 1   is index n! -1
+**
+** The actual values of the elements are immaterial, only the relative
+** ordering of the values is used.
+**
+** pit[] is the array of elements of length size.
+** The return value is the permutation index.
+*/
+
+int perm_index (char pit[], int size)
+{
+      int i;
+      register int j, ball;
+      int index = 0;
+
+      for (i = 1; i < size; i++)
+      {
+            ball = pit[i-1];
+            for (j = i; j < size; j++)
+            {
+                  if (ball > pit[j])
+                        index ++;
+            }
+            index *= size - i;
+      }
+      return index;
+}