1 files changed, 33 insertions, 1 deletions

diff --git a/apps/plugins/puzzles/src/towers.c b/apps/plugins/puzzles/src/towers.c
index a72cae680d..aee088fb54 100644
--- a/apps/plugins/puzzles/src/towers.c
+++ b/apps/plugins/puzzles/src/towers.c
@@ -574,6 +574,38 @@ static int solver_hard(struct latin_solver *solver, void *vctx)
 #define SOLVER(upper,title,func,lower) func,
 static usersolver_t const towers_solvers[] = { DIFFLIST(SOLVER) };
 
+static bool towers_valid(struct latin_solver *solver, void *vctx)
+{
+    struct solver_ctx *ctx = (struct solver_ctx *)vctx;
+    int w = ctx->w;
+    int c, i, n, best, clue, start, step;
+    for (c = 0; c < 4*w; c++) {
+        clue = ctx->clues[c];
+        if (!clue)
+            continue;
+
+        STARTSTEP(start, step, c, w);
+        n = best = 0;
+        for (i = 0; i < w; i++) {
+            if (solver->grid[start+i*step] > best) {
+                best = solver->grid[start+i*step];
+                n++;
+            }
+        }
+
+        if (n != clue) {
+#ifdef STANDALONE_SOLVER
+            if (solver_show_working)
+                printf("%*sclue %s %d is violated\n",
+                        solver_recurse_depth*4, "",
+                        cluepos[c/w], c%w+1);
+#endif
+            return false;
+        }
+    }
+    return true;
+}
+
 static int solver(int w, int *clues, digit *soln, int maxdiff)
 {
     int ret;
@@ -589,7 +621,7 @@ static int solver(int w, int *clues, digit *soln, int maxdiff)
     ret = latin_solver(soln, w, maxdiff,
                        DIFF_EASY, DIFF_HARD, DIFF_EXTREME,
                        DIFF_EXTREME, DIFF_UNREASONABLE,
-                       towers_solvers, &ctx, NULL, NULL);
+                       towers_solvers, towers_valid, &ctx, NULL, NULL);
 
     sfree(ctx.iscratch);
     sfree(ctx.dscratch);