My code exited after I filled up the priority queue - c++

Question

The code is about Huffman code.
I typed in "6 a 16 b 5 c 12 d 17 e 10 f 25", to fill in the priority_queue and the program exited without an error.
The priority queue is used to set up a binary search tree for decoding.
I made a function storeBinayNumber() to store the code for each character into an unordered map
called HuffmanCode , which is used for encoding;
and two function encocde() and decode() to encode or decode the string that will be later typed in .
What might be the problem ?
#include <iostream>
#include <queue>
#include <unordered_map>
#include <vector>
using namespace std;
class Node
{
public:
char ch = '\0';
int freq = 0;
Node *left;
Node *right;
};
void storeBinaryNumber(Node *root, unordered_map<char, string> &HuffmanCode, string str = '\0')
{
if (root = nullptr)
return;
if (!root->left && !root->right)
HuffmanCode[root->ch] = str;
storeBinaryNumber(root->left, HuffmanCode, str + "0");
storeBinaryNumber(root->right, HuffmanCode, str + "1");
}
void decode(Node *root, Node *current, string str, int index = 0)
{
if (index > str.length() - 1)
{
if (current == root)
{
cout << "Decoding suceeded" << endl;
return;
}
else
cout << "Invalid code" << endl;
return;
}
if (!current->left && !current->right)
{
cout << current->ch;
decode(root, root, str, index + 1);
}
else if (str[index] == '0')
{
decode(root, current->left, str, index + 1);
}
else if (str[index] == '1')
{
decode(root, current->right, str, index + 1);
}
}
void encode(string str, unordered_map<char, string> HuffmanCode)
{
for (int i = 0; i < str.length(); i++)
{
cout << HuffmanCode[str[i]];
}
}
int main()
{
int num;
cin >> num; //6 a 16 b 5 c 12 d 17 e 10 f 25
auto compare = [](Node *a, Node *b) //lambda expression
{ return a->freq > b->freq; };
priority_queue<Node *, vector<Node *>, decltype(compare)> q(compare);
unordered_map<char, string> HuffmanCode;
char character;
int frequency;
for (int i = 1; i <= num; i++)
{
cin >> character >> frequency;
Node *node = new Node;
node->ch = character;
node->freq = frequency;
node->left = nullptr;
node->right = nullptr;
q.push(node);
}
Node *root;
while (q.size() > 1)
{
Node *A = q.top();
q.pop();
Node *B = q.top();
q.pop();
Node *C = new Node;
C->left = A;
C->right = B;
C->freq = A->freq + B->freq;
if (q.empty())
root = C;
q.push(C);
}
storeBinaryNumber(root, HuffmanCode);
int en_or_de;
string input;
cout << "press 1 to encode , press 2 to decode." << endl;
cin >> en_or_de;
cout << "input: " << endl;
cin >> input;
if (en_or_de == 1)
{
encode(input, HuffmanCode);
}
else
decode(root, root, input);
system("pause");
return 0;
}

Answer 1

The code have several bugs:
Assign char type to string won't compile on my compiler
void storeBinaryNumber(Node *root, unordered_map<char, string> &HuffmanCode, string str = '\0')
The comparison should use ==, this seems to be a typo.
if (root = nullptr)
And the Node type missed destructor, which needs to a memory leak. After my fix the code seems to work. But it may still have logic bugs.
#include <iostream>
#include <queue>
#include <unordered_map>
#include <vector>
using namespace std;
class Node {
public:
char ch = '\0';
int freq = 0;
~Node() {
delete left;
delete right;
}
Node *left;
Node *right;
};
void storeBinaryNumber(Node *root, unordered_map<char, string> &HuffmanCode,
string str = "") {
if (root == nullptr) return;
if (!root->left && !root->right) HuffmanCode[root->ch] = str;
storeBinaryNumber(root->left, HuffmanCode, str + "0");
storeBinaryNumber(root->right, HuffmanCode, str + "1");
}
void decode(Node *root, Node *current, string str, int index = 0) {
if (index > str.length() - 1) {
if (current == root) {
cout << "Decoding suceeded" << endl;
return;
}
else
cout << "Invalid code" << endl;
return;
}
if (!current->left && !current->right) {
cout << current->ch;
decode(root, root, str, index + 1);
}
else if (str[index] == '0') {
decode(root, current->left, str, index + 1);
}
else if (str[index] == '1') {
decode(root, current->right, str, index + 1);
}
}
void encode(string str, unordered_map<char, string> HuffmanCode) {
for (int i = 0; i < str.length(); i++) {
cout << HuffmanCode[str[i]];
}
std::cout << std::endl;
}
int main() {
int num;
cin >> num; // 6 a 16 b 5 c 12 d 17 e 10 f 25
auto compare = [](Node *a, Node *b) // lambda expression
{ return a->freq > b->freq; };
priority_queue<Node *, vector<Node *>, decltype(compare)> q(compare);
unordered_map<char, string> HuffmanCode;
char character;
int frequency;
for (int i = 1; i <= num; i++) {
cin >> character >> frequency;
Node *node = new Node;
node->ch = character;
node->freq = frequency;
node->left = nullptr;
node->right = nullptr;
q.push(node);
}
Node *root;
while (q.size() > 1) {
Node *A = q.top();
q.pop();
Node *B = q.top();
q.pop();
Node *C = new Node;
C->left = A;
C->right = B;
C->freq = A->freq + B->freq;
if (q.empty()) root = C;
q.push(C);
}
storeBinaryNumber(root, HuffmanCode);
int en_or_de;
string input;
cout << "press 1 to encode , press 2 to decode." << endl;
cin >> en_or_de;
cout << "input: " << endl;
cin >> input;
if (en_or_de == 1) {
encode(input, HuffmanCode);
}
else
decode(root, root, input);
delete root;
// system("pause");
return 0;
}