Problems with quickSorting a QVector

[MaKoZer]

Hello,

i've some Problems in my Project with quickSorting a QVector.

Its just a simple pointer QVector and i want to sort it .... strangely the sort Algorithm works in another projekt very good ...

and SOMEHOW sometime it works, sometimes NOT .... thats so strange o0

Error Pic:
Error MSG:
ASSERT failure in QVector<T>::operator[]: "index out of range", file e:\programme\qtcpp\5.11.1\msvc2017_64\include\qtcore\qvector.h, line 436
16:31:09: The program has unexpectedly finished.
16:31:09: The process was ended forcefully.
16:31:09: [...] crashed.

You can find the whole project here:
https://github.com/Makozer/NpPartitionManager

The Code: (see vectorstash.cpp )

// Base Class
class VectorStash {
    typedef QVector<Coin*> CoinList;
public:
[...]
void quickSortDesc();
private:
[...]
void quickSortDesc(quint16 leftpos, quint16 rightpos);
CoinList coins;
};


// GUI just uses this simple method
void VectorStash::quickSortDesc() {
    if (coins.size() > 1) {
        quickSortDesc(0, (coins.size() - 1));
    }
}


// this method is called by the simple method
void VectorStash::quickSortDesc(quint16 leftpos, quint16 rightpos) {
    quint16 i = leftpos, j = rightpos;
    Coin* tmp;

    int pivot = coins[(leftpos + rightpos) / 2]->getValue();

    while (i <= j) {
        while (coins[i]->getValue() > pivot) { i++; }
        while (coins[j]->getValue() < pivot) { j--; }
        if (i <= j) {
            tmp = coins[i];
            coins[i] = coins[j];
            coins[j] = tmp;
            i++;
            j--;
        }
    };
    /* recursion */
    if (leftpos < j) { quickSortDesc(leftpos, j); }
    if (i < rightpos) { quickSortDesc(i, rightpos); }
} // end quickSortDesc

I cant see or find why im getting a "index out of range" error :(

the next problem is, as a new it student im used to programm on the console and im able to print me all useful steps so i can see where it crashes, here the real big problem is that i just get this error msg and program shuts down, no way to see better information on this bug ...

debugger wont works, too :/

does someone sees the problem? or has a useful tip how i can do bette rresearch on this bug?

thx =)

greetings

[mrjj]

Hi
In GUI programs you can use
qDebug() << "Text=" << variable;
which shows up inside qtCreator.

[VRonin]

Just delete your sort implementation. Why would anybody waste time implementing a custom sort?
if coins is of type QVector<Coin*> just use std::sort(coins.begin(),coins.end(),[](Coin* a, Coin* b)->bool{return return a->getValue() < b->getValue() ;});

[MaKoZer]

@mrjj said in Problems with quickSorting a QVector:

Hi
In GUI programs you can use
qDebug() << "Text=" << variable;
which shows up inside qtCreator.

thanks!!! i will try it =D

@VRonin said in Problems with quickSorting a QVector:

Just delete your sort implementation. Why would anybody waste time implementing a custom sort?
if coins is of type QVector<Coin*> just use std::sort(coins.begin(),coins.end(),[](Coin* a, Coin* b)->bool{return return a->getValue() < b->getValue() ;});

well, because we had to learn the algorithm in one module and i wanted to fully understand it so i wrote it :D
and i need it ascending and descending, depending how i choose, is that possible with std::sort? i guess so? :D
oh wait maybe i can do it in that case ... ill have a short look

thx for answers!

/edit
@VRonin
you're pretty right, thx a lot ... everything i wanted, but without bugs =D