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Update node ordering algorithm for huffman encoding

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This commit is contained in:
James Bowes 2012-09-06 15:55:17 -03:00
parent 3d94813dc8
commit 790d494da1
3 changed files with 43 additions and 22 deletions
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52
huffman.c
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@ -7,22 +7,17 @@
static int
find_smallest (struct huffman_node **nodes, int count, int different)
{
int smallest;
// 'real' weights will always be positive.
int smallest = -1;
int i;
for (i = 0; nodes[i]->weight == -1; i++);
if (i == different) {
for (i++; nodes[i]->weight == -1; i++);
}
smallest = i;
for (i = smallest + 1; i < count; i++) {
if (i == different || nodes[i]->weight == -1) {
for (i = 0; i < count; i++) {
if (i == different) {
continue;
}
if (nodes[i]->weight < nodes[smallest]->weight) {
if (smallest == -1 ||
nodes[i]->weight < nodes[smallest]->weight) {
smallest = i;
}
}
@ -30,6 +25,17 @@ find_smallest (struct huffman_node **nodes, int count, int different)
return smallest;
}
static void
shift_nodes (struct huffman_node **nodes, int count, int start)
{
int i;
for (i = start; i + 1 < count; i++) {
nodes[i] = nodes[i + 1];
}
nodes[i] = NULL;
}
struct huffman_node *
huffman_build_tree(void **values, int count)
{
@ -52,24 +58,30 @@ huffman_build_tree(void **values, int count)
int tree1;
int tree2;
for (i = 1; i < count; i++) {
for (; count > 1; count--) {
struct huffman_node *tmp;
tree1 = find_smallest (nodes, count, -1);
tree2 = find_smallest (nodes, count, tree1);
tmp = nodes[tree1];
tmp = malloc (sizeof (struct huffman_node));
tmp->weight = nodes[tree1]->weight + nodes[tree2]->weight;
tmp->value = NULL;
tmp->left = nodes[tree1];
tmp->right = nodes[tree2];
nodes[tree1] = malloc (sizeof (struct huffman_node));
nodes[tree1]->weight = tmp->weight + nodes[tree2]->weight;
nodes[tree1]->value = NULL;
nodes[tree1]->left = tmp;
nodes[tree1]->right = nodes[tree2];
if (tree1 > tree2) {
shift_nodes (nodes, count, tree1);
shift_nodes (nodes, count, tree2);
} else {
shift_nodes (nodes, count, tree2);
shift_nodes (nodes, count, tree1);
}
nodes[tree2]->weight = -1;
nodes[count - 2] = tmp;
}
return nodes[tree1];
return nodes[0];
}
void *