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+#! /usr/bin/env gforth
+
+\ Challenge 195
+\
+\ Task 2: Most Frequent Even
+\ Submitted by: Mohammad S Anwar
+\ You are given a list of numbers, @list.
+\
+\ Write a script to find most frequent even numbers in the list. In case you
+\ get more than one even numbers then return the smallest even integer. For all
+\ other case, return -1.
+\
+\ Example 1
+\ Input: @list = (1,1,2,6,2)
+\ Output: 2 as there are only 2 even numbers 2 and 6 and of those 2 appears
+\ the most.
+\ Example 2
+\ Input: @list = (1,3,5,7)
+\ Output: -1 since no even numbers found in the list
+\ Example 3
+\ Input: @list = (6,4,4,6,1)
+\ Output: 4 since there are only two even numbers 4 and 6. They both appears
+\ the equal number of times, so pick the smallest.
+
+CREATE nums 256 CELLS ALLOT
+0 VALUE nums_size
+
+: nums[] ( idx -- addr )
+    CELLS nums +
+;
+
+: collect_args ( -- )
+    BEGIN NEXT-ARG DUP WHILE
+        0 0 2SWAP >NUMBER 2DROP DROP
+        nums_size nums[] !
+        nums_size 1+ TO nums_size
+    REPEAT
+    2DROP
+;
+
+: max_nums ( -- n )
+    0
+    nums_size 0 ?DO
+        I nums[] @ MAX
+    LOOP
+;
+
+0 VALUE hist
+0 VALUE hist_size
+
+: hist[] ( idx -- addr )
+    CELLS hist +
+;
+
+: make_hist ( -- )
+    max_nums 1+ DUP TO hist_size
+    CELLS ALLOCATE THROW TO hist
+    hist hist_size CELLS ERASE
+    nums_size 0 ?DO
+        I nums[] @  hist[]  1 SWAP +!
+    LOOP
+;
+
+: max_even ( -- )
+    make_hist
+    -1 0            ( n max )
+    hist_size 0 ?DO
+        I hist[] @ OVER > IF
+            2DROP I I hist[] @
+        THEN
+    2 +LOOP
+    DROP
+;
+
+collect_args
+max_even . CR
+BYE