Add Forth solutions

2 files changed, 114 insertions, 0 deletions

diff --git a/challenge-243/paulo-custodio/forth/ch-1.fs b/challenge-243/paulo-custodio/forth/ch-1.fs
new file mode 100644
index 0000000000..5325b2cc8b
--- /dev/null
+++ b/challenge-243/paulo-custodio/forth/ch-1.fs
@@ -0,0 +1,58 @@
+#! /usr/bin/env gforth
+
+\ Challenge 243
+\
+\ Task 1: Reverse Pairs
+\ Submitted by: Mohammad S Anwar
+\ You are given an array of integers.
+\
+\ Write a script to return the number of reverse pairs in the given array.
+\
+\ A reverse pair is a pair (i, j) where: a) 0 <= i < j < nums.length and b) nums[i] > 2 * nums[j].
+\
+\ Example 1
+\ Input: @nums = (1, 3, 2, 3, 1)
+\ Output: 2
+\
+\ (1, 4) => nums[1] = 3, nums[4] = 1, 3 > 2 * 1
+\ (3, 4) => nums[3] = 3, nums[4] = 1, 3 > 2 * 1
+\ Example 2
+\ Input: @nums = (2, 4, 3, 5, 1)
+\ Output: 3
+\
+\ (1, 4) => nums[1] = 4, nums[4] = 1, 4 > 2 * 1
+\ (2, 4) => nums[2] = 3, nums[4] = 1, 3 > 2 * 1
+\ (3, 4) => nums[3] = 5, nums[4] = 1, 5 > 2 * 1
+
+CREATE nums 256 CELLS ALLOT
+0 VALUE nums_size
+
+: nums[] ( i -- 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
+;
+
+: count_reverse_pairs ( -- n )
+    0 { count }
+    nums_size 1- 0 DO
+        nums_size I 1+ DO
+            J nums[] @  I nums[] @ 2* > IF
+                count 1+ TO count
+            THEN
+        LOOP
+    LOOP
+    count
+;
+
+\ main
+collect_args
+count_reverse_pairs . CR
+BYE
diff --git a/challenge-243/paulo-custodio/forth/ch-2.fs b/challenge-243/paulo-custodio/forth/ch-2.fs
new file mode 100644
index 0000000000..d762dbf362
--- /dev/null
+++ b/challenge-243/paulo-custodio/forth/ch-2.fs
@@ -0,0 +1,56 @@
+#! /usr/bin/env gforth
+
+\ Challenge 243
+\
+\ Task 1: Reverse Pairs
+\ Submitted by: Mohammad S Anwar
+\ You are given an array of integers.
+\
+\ Write a script to return the number of reverse pairs in the given array.
+\
+\ A reverse pair is a pair (i, j) where: a) 0 <= i < j < nums.length and b) nums[i] > 2 * nums[j].
+\
+\ Example 1
+\ Input: @nums = (1, 3, 2, 3, 1)
+\ Output: 2
+\
+\ (1, 4) => nums[1] = 3, nums[4] = 1, 3 > 2 * 1
+\ (3, 4) => nums[3] = 3, nums[4] = 1, 3 > 2 * 1
+\ Example 2
+\ Input: @nums = (2, 4, 3, 5, 1)
+\ Output: 3
+\
+\ (1, 4) => nums[1] = 4, nums[4] = 1, 4 > 2 * 1
+\ (2, 4) => nums[2] = 3, nums[4] = 1, 3 > 2 * 1
+\ (3, 4) => nums[3] = 5, nums[4] = 1, 5 > 2 * 1
+
+CREATE nums 256 CELLS ALLOT
+0 VALUE nums_size
+
+: nums[] ( i -- 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
+;
+
+: sum_floor ( -- n )
+    0 { sum }
+    nums_size 0 DO
+        nums_size 0 DO
+            sum  J nums[] @  I nums[] @  /  +  TO sum
+        LOOP
+    LOOP
+    sum
+;
+
+\ main
+collect_args
+sum_floor . CR
+BYE