The Question is how can the code has mistakes when it runs correctly in Qt with the same array as input as in example.

Because you didn´t replay anything that could solve the problem

Hi everyone. When I run the code in my IDE(Qt) it shows the correct output, but when I run the code here, I get different output. Does someone encountered similar problem?

int findOdd(const std::vector<int>& numbers) {

int arrayLength = numbers.size(); 
for(int i = 0; i < (arrayLength - 1); i++) {
    int counter = 0;
    for(int j = 0; j <= arrayLength; j++) {
        if (numbers[i] == numbers[j]) {
            counter++;
        }
    }
    if(counter % 2) {
        return numbers[i];
    }
}
return numbers[arrayLength - 1];

}

When I test this code in Qt with sample arrays it returns the correct value, but when I execute it here it doesn't. Any ideas why.