pat 05-树9 Huffman Codes

最新推荐文章于 2021-08-10 21:14:22 发布

王莞原

最新推荐文章于 2021-08-10 21:14:22 发布

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分类专栏：数据结构

本文链接：https://blog.youkuaiyun.com/qq_36988616/article/details/72802417

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本文介绍了一种使用优先队列构建哈夫曼树的方法，并实现了一个验证给定编码是否为最优编码的程序。文章详细解释了哈夫曼树的构建过程、节点权重计算、树的深度设置以及如何计算最小成本。

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#include <iostream>
#include <algorithm>
#include <queue>
#include <vector>
#include <functional>
#include <cstring>
#include <map>
#include <climits>
using namespace std;
typedef struct BiTNode {
	char key;
	int weight;
	BiTNode *lchild, *rchild;
	BiTNode(char k = '\0', int w = 0, BiTNode* l = NULL, BiTNode* r = NULL) : key(k), weight(w), lchild(l), rchild(r) {}
} *BiTree;
struct cmp {
	bool operator() (const BiTree& a, const BiTree& b)
	{
		return a->weight > b->weight;
	}
};
priority_queue<BiTree, vector<BiTree>, cmp> q;
int N;
char key[64];
int frequence[CHAR_MAX + 5];
int depth[CHAR_MAX + 5];
bool flag = true;
BiTree BuildHaffmanTree() 
{
	BiTree T;
	while (q.size() > 1)
	{
		T = new BiTNode();
		T->lchild = q.top();
		q.pop();
		T->rchild = q.top();
		q.pop();
		T->weight = T->lchild->weight + T->rchild->weight;
		q.push(T);
	}
	return T;
}

void setdepth(BiTree T, int d)
{
	if (!T)
		return;
	depth[T->key] = d;
	setdepth(T->lchild, d + 1);
	setdepth(T->rchild, d + 1);
}
void destroyTree(BiTree T)
{
	if (!T)
		return;
	destroyTree(T->lchild);
	destroyTree(T->rchild);
	delete T;
}
BiTree insert(BiTree& T, const char *path)
{
	if (*path == '\0')
		return NULL;
	if (*path == '0')
	{
		
	}
}
int get_minicost(BiTree T)
{
	int minicost = 0;
	setdepth(T, 0);
	for (int i = 0; i < N; ++i)
	{
		minicost += depth[key[i]] * frequence[key[i]];
	}
	return minicost;
}
int main(void)
{
	freopen("in.txt", "r", stdin);
	freopen("out.txt", "w", stdout);
	BiTree Tree;
	char code[64][64];
	int n, w;
	char k;
	cin >> N;
	for (int i = 0; i < N; ++i)
	{
		cin >> key[i] >> w; 
		frequence[key[i]] = w;
		Tree = new BiTNode(key[i], w);
		q.push(Tree);
	}
	Tree = BuildHaffmanTree();
	int minicost = get_minicost(Tree);
	destroyTree(Tree);

	cin >> n;
	while (n--)
	{
		flag = true;
		BiTree root = new BiTNode();
		int cur_cost = 0;

		for (int i = 0; i < N; ++i)
		{
			cin >> key[i] >> code[i];
			cur_cost += frequence[key[i]] * strlen(code[i]);
		}
		

		if (cur_cost != minicost)
			flag = false;
		else
		{
			for (int i = 0; i < N && flag; ++i)
			{
				BiTree *cur = &root;	//这样才能改变root
				int len = strlen(code[i]);
				for (int j = 0; j < len; ++j)
				{
					if (code[i][j] == '0')
						cur = &(*cur)->lchild;
					else
						cur = &(*cur)->rchild;
					if (!*(cur))
						*cur = new BiTNode();
					else if (j + 1 < len)
						continue;
					else
					{
						flag = false;
						break;
					}
				}
			}
		}
		cout << (flag ? "Yes" : "No") << endl;
		destroyTree(root);
	}

	return 0;
}