ocaml: phase 5.1 coin_min.ml baseline (67 cents in US coins = 6)

Minimum-coin DP with -1 sentinel for unreachable values:

  let coin_min coins amount =
    let dp = Array.make (amount + 1) (-1) in
    dp.(0) <- 0;
    for i = 1 to amount do
      List.iter (fun c ->
        if c <= i && dp.(i - c) >= 0 then begin
          let cand = dp.(i - c) + 1 in
          if dp.(i) < 0 || cand < dp.(i) then dp.(i) <- cand
        end
      ) coins
    done;
    dp.(amount)

  coin_min [1; 5; 10; 25] 67 = 6   (* 25+25+10+5+1+1 *)

Tests `if c <= i && dp.(i-c) >= 0 then` short-circuit guard;
relies on iter-242 fix so dp.(i-c) is not evaluated when c > i.

158 baseline programs total.

lib/ocaml/baseline/coin_min.ml

@@ -0,0 +1,16 @@
+let coin_min coins amount =
+  let dp = Array.make (amount + 1) (-1) in
+  dp.(0) <- 0;
+  for i = 1 to amount do
+    List.iter (fun c ->
+      if c <= i && dp.(i - c) >= 0 then begin
+        let cand = dp.(i - c) + 1 in
+        if dp.(i) < 0 || cand < dp.(i) then dp.(i) <- cand
+      end
+    ) coins
+  done;
+  dp.(amount)
+
+;;
+
+coin_min [1; 5; 10; 25] 67

lib/ocaml/baseline/expected.json

@@ -25,6 +25,7 @@
   "catalan.ml": 42,
   "closures.ml": 315,
   "coin_change.ml": 6,
+  "coin_min.ml": 6,
   "count_change.ml": 406,
   "count_inversions.ml": 12,
   "csv.ml": 10,

plans/ocaml-on-sx.md

@@ -407,6 +407,13 @@ _Newest first._
   binary search tree (`type 'a tree = Leaf | Node of 'a * 'a tree *
   'a tree`) with insert + in-order traversal. Tests parametric ADT,
   recursive match, List.append, List.fold_left.
+- 2026-05-10 Phase 5.1 — coin_min.ml baseline (minimum-coin change
+  for 67¢ with US denominations = 6 coins). DP with -1 sentinel
+  for unreachable values: `dp.(i) := min over coins c of dp.(i-c)+1
+  when dp.(i-c) >= 0`. 67 = 25+25+10+5+1+1 = 6 coins. Tests `if
+  c <= i && dp.(i - c) >= 0 then …` guard short-circuit; without
+  iter-242 fix the dp.(i-c) read would crash for c > i. 158
+  baseline programs total.
 - 2026-05-10 Phase 5.1 — flood_fill.ml baseline (largest connected
   component in 5×5 grid = 7). Recursive 4-direction flood from
   every unvisited 1-cell; bounds check short-circuits before the