C语言中压缩字符串的简单算法小结

unsigned long HashString(const char *pString, unsigned long tableSize)
{
 unsigned long hashValue = 0;
 while(*pString)
    hashValue += *pString++;
 return hashValue % tableSize;
}

unsigned long HashString(const char *pString,unsigned long tableSize)
{
 unsigned long hashValue = 0;
 while (*pString)
 hashValue = (hashValue << 5) + *pString++;
 return hashValue % tableSize;
}

#define Size 10 
int freq[Size]; 
string code[Size]; 
string word; 
struct Node 
{ 
 int id; 
 int freq; 
 Node *left; 
 Node *right; 
 Node(int freq_in):id(-1), freq(freq_in) 
 { 
  left = right = NULL; 
 } 
}; 
struct NodeLess 
{ 
 bool operator()(const Node *a, const Node *b) const 
 { 
  return a->freq < b->freq; 
 } 
}; 
 
void init() 
{ 
 for(int i = 0; i < Size; ++i) 
  freq[i] = 0; 
 for(int i = 0; i < word.size(); ++i) 
  ++freq[word[i]]; 
} 
void dfs(Node *root, string res) 
{ 
 if(root->id >= 0) 
  code[root->id] = res; 
 else 
 { 
  if(NULL != root->left) 
   dfs(root->left, res+"0"); 
  if(NULL != root->right) 
   dfs(root->right, res+"1"); 
 } 
} 
 
void deleteNodes(Node *root) 
{ 
 if(NULL == root) 
  return ; 
 if(NULL == root->left && NULL == root->right) 
  delete root; 
 else 
 { 
  deleteNodes(root->left); 
  deleteNodes(root->right); 
  delete root; 
 } 
} 
void BuildTree() 
{ 
 priority_queue<Node*, vector<Node*>, NodeLess> nodes; 
 for(int i = 0; i < Size; ++i) 
 { 
//0 == freq[i] 的情况未处理 
    Node *newNode = new Node(freq[i]); 
  newNode->id = i; 
  nodes.push(newNode); 
 } 
 while(nodes.size() > 1) 
 { 
  Node *left = nodes.top(); 
  nodes.pop(); 
  Node *right = nodes.top(); 
  nodes.pop(); 
  Node *newNode = new Node(left->freq + right->freq); 
    newNode->left = left; 
    newNode->right = right; 
    nodes.push(newNode); 
 } 
 Node *root = nodes.top(); 
 dfs(root, string("")); 
 deleteNodes(root); 
}