Getting problem with priority queue in cpp

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I was studying huffman coding ,I faced a problem while dealing with priority queue

Here is the code[^]

What I have tried:

I tried to make some changes that i have learned so far in cpp
in above cpp program i changed below part of code

C++

struct Node
    {
    	char ch;
    	int freq;
    	Node *left, *right;
    };


    struct comp
    {
    	bool operator()(Node* l, Node* r)
    	{
    		// highest priority item has lowest frequency
    		return l->freq > r->freq;
     	}
   };

and using as

C++

`priority_queue<Node*, vector<Node*>, comp> pq`

in `buidingHuffmanTree()` function.

i changed it to

C++

struct Node
    {
        char ch; 
        int freq;
        Node *left, *right;
        bool operator<(Node const* other) {
        return freq < other->freq;
    }
    };

Now i tried to use like

C++

`priority_queue<Node*, vector<Node*>> pq`

But I am getting wrong answers. In above program input is static you can see that
answers is exactly (input output is large i can't write here )

Also tried to change the signs as `freq > other.freq` instead of `<` getting wrong answers

Is both pieces of code are working differently,I thought they will work in same way.

[1]: https://www.techiedelight.com/huffman-coding/

Posted 10-Jun-19 0:43am

kavinderrana121

Updated 10-Jun-19 3:40am

v2

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CPallini 10-Jun-19 7:19am

I see no code in the linked page.

1 solution

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Patrice T · Answer 1 · 2019-06-10T03:40:00

Quote:
I faced a problem while dealing with priority queue

It is better to show your code and describe the problem you faced. the link is wrong, there is no code.

Your code do not behave the way you expect, or you don't understand why !

There is an almost universal solution: Run your code on debugger step by step, inspect variables.
The debugger is here to show you what your code is doing and your task is to compare with what it should do.
There is no magic in the debugger, it don't know what your code is supposed to do, it don't find bugs, it just help you to by showing you what is going on. When the code don't do what is expected, you are close to a bug.
To see what your code is doing: Just set a breakpoint and see your code performing, the debugger allow you to execute lines 1 by 1 and to inspect variables as it execute.

Debugger - Wikipedia, the free encyclopedia[^]

Mastering Debugging in Visual Studio 2010 - A Beginner's Guide[^]
Basic Debugging with Visual Studio 2010 - YouTube[^]

1.11 — Debugging your program (stepping and breakpoints) | Learn C++[^]

The debugger is here to only show you what your code is doing and your task is to compare with what it should do.