c++ overflow, merge sorting, inversion calculator

Question

My code is to calculate the number of inversion in the array. The calculation is working fine. The problem is that normally the range of unsigned int is 4,294,967,295 but it only accept the range of 2,147,483,647, equivalently, it doesn't recognize unsigned data type, instead accept it as signed.

unsigned int _mergeSort(int arr[], int temp[], unsigned int left, unsigned int right);
unsigned int merge(int arr[], int temp[], unsigned int left, unsigned int mid, unsigned int right);

unsigned int mergeSort(int arr[], int array_size) {
    int *temp = (int *)malloc(sizeof(int)*array_size);
    return _mergeSort(arr, temp, 0, array_size - 1);
}

unsigned int _mergeSort(int arr[], int temp[], unsigned int left, unsigned int right) {
    unsigned int mid;
    unsigned int inv_count = 0;
    if (right > left)   {

        mid = (right + left) / 2;

        inv_count = _mergeSort(arr, temp, left, mid);

        inv_count += _mergeSort(arr, temp, mid + 1, right);

        inv_count += merge(arr, temp, left, mid + 1, right);
    }
    return inv_count;
}

unsigned int merge(int arr[], int temp[], unsigned int left, unsigned int mid, unsigned int right) {
    unsigned int i, j, k;
    unsigned int inv_count = 0;
    i = left;
    j = mid; 
    k = left; 
    while ((i <= mid - 1) && (j <= right)) {
        if (arr[i] <= arr[j]) {
            temp[k++] = arr[i++];
        } else {
            temp[k++] = arr[j++];
            inv_count = inv_count + (mid - i);
        }
    }
        while (i <= mid - 1)
            temp[k++] = arr[i++];
        while (j <= right)
            temp[k++] = arr[j++];
        for (i = left; i <= right; i++)
            arr[i] = temp[i];
    return inv_count;
}

int main(int argv, char** args) {
    const int size = 100000;
    int arr[size];
    unsigned int i = 0;
    int converted;

    string input;
    fstream dataFile("IntegerArray.txt", ios::in);
    if (dataFile) {
        getline(dataFile, input);
        while (dataFile) {
            converted = atoi(input.c_str());
            arr[i++] = converted;           
            getline(dataFile, input);
        }
        dataFile.close();
    } else {
        cout << "error" << endl;
    }

    printf("Number of inversions are %d \n", mergeSort(arr, i));
    getchar();
    return 0;
}

Answer 1

In your call to printf() you use a format specifier of %d which means signed integer . The actual value passed is an unsigned integer and the correct format specifier for that is %u . Fix the printf() call and test again.

Here is a reference for printf() and its formatting options.