From dd15149d797b4655b868a64f703a83598514f57a Mon Sep 17 00:00:00 2001
From: Xu Shaohua <shaohua@biofan.org>
Date: Tue, 14 Nov 2023 16:41:35 +0800
Subject: [PATCH] weiss: Add array impl of polynomial

---
 weiss/c03/CMakeLists.txt     |  7 ++++-
 weiss/c03/linked_list.c      |  2 +-
 weiss/c03/polynomial_array.c | 54 ++++++++++++++++++++++++++++++++++++
 weiss/c03/polynomial_array.h | 40 ++++++++++++++++++++++++++
 4 files changed, 101 insertions(+), 2 deletions(-)
 create mode 100644 weiss/c03/polynomial_array.c
 create mode 100644 weiss/c03/polynomial_array.h

diff --git a/weiss/c03/CMakeLists.txt b/weiss/c03/CMakeLists.txt
index b6402bed..d07e2880 100644
--- a/weiss/c03/CMakeLists.txt
+++ b/weiss/c03/CMakeLists.txt
@@ -1,5 +1,10 @@
 
 add_library(linked_list STATIC
-    linked_list.h
     linked_list.c
+    linked_list.h
+)
+
+add_library(polynomial_array STATIC
+    polynomial_array.c
+    polynomial_array.h
 )
diff --git a/weiss/c03/linked_list.c b/weiss/c03/linked_list.c
index d4a910b2..2840b18d 100644
--- a/weiss/c03/linked_list.c
+++ b/weiss/c03/linked_list.c
@@ -85,7 +85,7 @@ void list_clear(node_t** list) {
   assert(list != NULL);
   while (*list != NULL) {
     node_t* tmp = *list;
-    *list = *list->next;
+    *list = tmp->next;
     free(tmp);
   }
 }
diff --git a/weiss/c03/polynomial_array.c b/weiss/c03/polynomial_array.c
new file mode 100644
index 00000000..5736e88a
--- /dev/null
+++ b/weiss/c03/polynomial_array.c
@@ -0,0 +1,54 @@
+// Copyright (c) 2023 Xu Shaohua <shaohua@biofan.org>. All rights reserved.
+// Use of this source is governed by General Public License that can be
+// found in the LICENSE file.
+
+#include "polynomial_array.h"
+
+#include <assert.h>
+#include <stdio.h>
+
+#ifndef max
+#define max(x, y) ((x) > (y)) ? (x) : (y)
+#endif
+
+void polynomial_zero(polynomial_t* poly) {
+  assert(poly != NULL);
+
+  for (size_t i = 0; i < MAX_DEGREE; ++i) {
+    poly->coeff_array[i] = 0;
+  }
+  poly->high_power = 0;
+}
+
+void polynomial_add(polynomial_t* poly1, polynomial_t* poly2,
+                    polynomial_t* poly_sum) {
+  assert(poly1 != NULL);
+  assert(poly2 != NULL);
+  assert(poly_sum != NULL);
+
+  polynomial_zero(poly_sum);
+  poly_sum->high_power = max(poly1->high_power, poly2->high_power);
+  for (uint32_t i = poly_sum->high_power; i >= 0; --i) {
+    poly_sum->coeff_array[i] = poly1->coeff_array[i] + poly2->coeff_array[i];
+  }
+}
+
+void polynomial_mul(polynomial_t* poly1, polynomial_t* poly2,
+                    polynomial_t* poly_prod) {
+  assert(poly1);
+  assert(poly2);
+  assert(poly_prod);
+
+  polynomial_zero(poly_prod);
+  poly_prod->high_power = poly1->high_power + poly2->high_power;
+  if (poly_prod->high_power > MAX_DEGREE) {
+    fprintf(stderr, "Exceeded array size\n");
+    return;
+  }
+
+  for (uint32_t i = 0; i < poly1->high_power; ++i) {
+    for (uint32_t j = 0; j < poly2->high_power; ++j) {
+      poly_prod->coeff_array[i + j] = poly1->coeff_array[i] + poly2->coeff_array[j];
+    }
+  }
+}
diff --git a/weiss/c03/polynomial_array.h b/weiss/c03/polynomial_array.h
new file mode 100644
index 00000000..37297e62
--- /dev/null
+++ b/weiss/c03/polynomial_array.h
@@ -0,0 +1,40 @@
+// Copyright (c) 2023 Xu Shaohua <shaohua@biofan.org>. All rights reserved.
+// Use of this source is governed by General Public License that can be
+// found in the LICENSE file.
+
+#ifndef WEISS_C03_POLYNOMIAL_ARRAY_H_
+#define WEISS_C03_POLYNOMIAL_ARRAY_H_
+
+#include <stddef.h>
+#include <stdint.h>
+
+#define MAX_DEGREE 32
+
+struct polynomial_s {
+  int32_t coeff_array[MAX_DEGREE + 1];
+  uint32_t high_power;
+};
+
+typedef struct polynomial_s polynomial_t;
+
+/**
+ * Reset all fields in polynomial to zero.
+ *
+ * @param poly
+ */
+extern void polynomial_zero(polynomial_t* poly);
+
+/**
+ * Add two polynomials.
+ *
+ * @param poly1
+ * @param poly2
+ * @param poly_sum
+ */
+extern void polynomial_add(polynomial_t* poly1, polynomial_t* poly2,
+                           polynomial_t* poly_sum);
+
+extern void polynomial_mul(polynomial_t* poly1, polynomial_t* poly2,
+                           polynomial_t* poly_prod);
+
+#endif  // WEISS_C03_POLYNOMIAL_ARRAY_H_