哈夫曼樹

#include<iostream>
#include<vector>
#include<fstream>
#include<algorithm>
#include<cmath>
#include<queue>
#include<set>
#include<map>
#include<string>
#include<sstream>
using namespace std;
/*
	此程序是用來模擬哈夫曼編碼
*/
/*
	ch 用來儲存ASICC
	count用存儲字符的數目
	isal用來記錄編碼樹中的結點是否爲字母結點
	left，right 指向左右結點
*/
struct node {
	char ch;
	int count;
	bool isal;
	struct node* left;
	struct node* right;
};
/*
	此爲map<struct node*,vector<struct node*> cmp> Q中的比較關鍵字
*/
struct cmp {
	bool operator () (struct node* n1, struct node* n2)
	{
		return n2->count < n1->count;
	}
};
/*
	用優先隊列來生成哈夫曼樹
*/
struct node* Bulid(priority_queue<struct node*, vector<struct node*>, cmp> Q)
{
	if (Q.size() == 0) {
		return NULL;
	}
	else if (Q.size() == 1) {
		return Q.top();
	}
	do {
		struct node* n = new struct node;
		n->isal = false;
		n->left = Q.top();
		Q.pop();
		n->right = Q.top();
		Q.pop();
		n->count = n->left->count + n->right->count;
		Q.push(n);
	} while (Q.size() > 1);
	return Q.top();
}
/*
	用已經統計好的字符和其數量對應的映射關係，遞歸生成哈夫曼編碼
*/
void Code(struct node* root,string s, map<char, string>& Map)
{
	if (root) {
		if (root->isal == true) {
			Map[root->ch] = s;
		}
		Code(root->left, s + "0", Map);
		Code(root->right, s + "1", Map);
	}
}
/*
	將文件C:\\Users\\DELL\\Desktop\\in.txt中的內容讀入，進行編碼並輸出到C:\\Users\\DELL\\Desktop\\out.txt
*/
void Encrypte(map<char, string> Map)
{
	ifstream inFile("C:\\Users\\DELL\\Desktop\\in.txt", ios::in);
	ofstream out("C:\\Users\\DELL\\Desktop\\out.txt", ios::out);
	char ch;
	string s;
	while (getline(inFile, s)) {
		for (size_t i = 0; i < s.size(); ++i) {
			ch = s[i];
			out << Map[ch];
		}
	}
	out.close();
	inFile.close();
}
/*
	對文件C:\\Users\\DELL\\Desktop\\out.txt中的內容進行解碼，並輸出到控制檯
*/
void Decrypt(map<char, string> Map)
{
	map<string, char> M;
	for (map<char, string>::iterator it = Map.begin(); it != Map.end(); ++it) {
		M[it->second] = it->first;
	}
	string s = "";
	ifstream inFile("C:\\Users\\DELL\\Desktop\\out.txt", ios::in);
	ofstream out("C:\\Users\\DELL\\Desktop\\in1.doc", ios::out);
	char ch;
	while (inFile >> ch) {
		s += ch;
		map<string, char>::iterator it = M.find(s);
		if (it != M.end()) {
			out << it->second;
			cout << it->second;
			s = "";
		}
	}
	cout << endl;

	inFile.close();
	out.close();
}

int main()
{
	ifstream inFile("C:\\Users\\DELL\\Desktop\\in.txt", ios::in);
	char ch;
	string s;
	map<char, int> Map;
	//將文件中的字符進行統計，並生成映射表
	while (getline(inFile, s)) {
		for (size_t i = 0; i < s.size(); ++i) {
			
			ch = s[i];
			if (Map.find(ch) == Map.end()) {
				Map[ch] = 1;
			}
			else {
				Map[ch]++;
			}
		}
	}
	inFile.close();


	//將映射表中的內容，轉變爲哈夫曼樹結點，爲生成哈夫曼樹進行初步
	priority_queue<struct node*, vector<struct node*>, cmp> Q;
	for (map<char, int>::iterator it = Map.begin(); it != Map.end(); ++it) {
		struct node* n=new struct node;
		n->isal = true;
		n->ch = it->first;
		n->count = it->second;
		n->left = n->right = NULL;
		Q.push(n);
	}
	struct node* root = Bulid(Q);
	map<char, string> Map1;
	Code(root, "", Map1);
	Encrypte(Map1);

	Decrypt(Map1);


/*
	for (map<char, string>::iterator it = Map1.begin(); it != Map1.end(); ++it) {
		cout << it->first << "	" << it->second << endl;
	}
	*/
	system("pause");
	return 0;
}