MissingInteger.c

// 22/100 SCORE
void swap(int* a, int* b)
{
    int temp;
    temp = *a;
    *a = *b;
    *b = temp;
}

int segregate(int arr[], int size)
{
    int j = 0, i;
    for (i = 0; i < size; i++) {
        if (arr[i] <= 0) {
            swap(&arr[i], &arr[j]);
            j++; // increment count of non-positive integers
        }
    }
    
    return j;
}

int findMissingPositive(int arr[], int size)
{
    int i;
    
    for (i = 0; i < size; i++) {
        if (abs(arr[i]) - 1 < size && arr[abs(arr[i]) - 1] > 0)
            arr[abs(arr[i]) - 1] = -arr[abs(arr[i]) - 1];
    }
    
    for (i = 0; i < size; i++)
        if (arr[i] > 0)
            return i + 1;
    
    return size + 1;
}

int findMissing(int arr[], int size)
{
    int shift = segregate(arr, size);
    
    return findMissingPositive(arr + shift, size - shift);
}

int solution(int A[], int N) {
    // Get Missing Integer
    int arr_size = N / A[0];
    int missing = findMissing(A, arr_size);
    return abs(missing);
}