long long inversions(It lo, It hi) {
if (hi - lo < 2) {
return 0;
}
It mid = lo + (hi - lo - 1)/2, a = lo, c = mid + 1;
long long res = 0;
res += inversions(lo, mid + 1);
res += inversions(mid + 1, hi);
typedef typename std::iterator_traits<It>::value_type T;
std::vector<T> merged;
while (a <= mid && c < hi) {
if (*c < *a) {
merged.push_back(*(c++));
res += (mid - a) + 1;
} else {
merged.push_back(*(a++));
}
}
if (a > mid) {
for (It it = c; it != hi; ++it) {
merged.push_back(*it);
}
} else {
for (It it = a; it <= mid; ++it) {
merged.push_back(*it);
}
}
for (It it = lo; it != hi; ++it) {
*it = merged[it - lo];
}
return res;
}
long long inversions(long start, long end)
{
long mid;
if (end - start < 2)
return 0;
mid = (start + end) / 2;
return inversions(start, mid) + inversions(mid, end) + merge(start, mid, end);
}
int main() {
{
int a[] = {6, 9, 1, 14, 8, 12, 3, 2};
assert(inversions(a, a + 8) == 16);
}
{
int a[] = {6, 9, 1, 14, 8, 12, 3, 2};
assert(inversions(8, a) == 16);
}
return 0;
}
int main(const int argc, const char* const argv[]) {
const Input_types mode =
(argc == 1) ? sin : (argc >= 3) ? s2m(argv[2]) : rdm;
index_t N;
try {
N = (argc >= 2) ? std::stoul(argv[1]) : 0;
}
catch (const std::invalid_argument& e) {
std::cerr << err << " N not a number: \"" << argv[1] << "\"\n";
return err_N1;
}
catch (const std::out_of_range& e) {
std::cerr << err << " N not in range: \"" << argv[1] << "\"\n";
return err_N2;
}
std::cout << "Mode = " << m2s(mode) << "." << std::endl;
if (mode != sin) std::cout << "N = " << N << "." << std::endl;
vec_t V;
try { V.reserve(N); }
catch(const std::bad_alloc& e) {
std::cerr << err << " N too large for memory: " << argv[1] << "\n";
return err_N3;
}
switch (mode) {
case sin :
for (int_t i; std::cin >> i; ++N) V.push_back(i);
std::cout << "N = " << N << "." << std::endl;
break;
case rdm :
std::srand(std::time(0));
for (index_t i = 0; i != N; ++i) V.push_back(std::rand());
break;
case ord :
for (index_t i = 0; i != N; ++i) V.push_back(i);
break;
case invord : {
index_t i = N;
while (i != 0) V.push_back(--i);
break;
}
}
std::cout << "Inversion count by definition: "; std::cout.flush();
auto start = std::chrono::system_clock::now();
std::cout << inversions_bydef(V) << "\n";;
std::cout << std::chrono::duration<double,std::milli>(std::chrono::system_clock::now() - start).count() << "ms" << std::endl;
std::cout << "Fast inversion count: "; std::cout.flush();
start = std::chrono::system_clock::now();
std::cout << inversions(V, 0, V.size()) << "\n";
std::cout << std::chrono::duration<double,std::milli>(std::chrono::system_clock::now() - start).count() << "ms" << std::endl;
}
long int inversions(long int arr[],long int high)
{
if(high<1)
return 0;
long int mid=(high+1)/2;
long int left[mid];
long int right[high-mid+1];
long int i,j;
for(i=0;i<mid;i++)
left[i]=arr[i];
for(i=high-mid,j=high;j>=mid;i--,j--)
right[i]=arr[j];
return inversions(left,mid-1) + inversions(right,high-mid) + merge(arr,left,right,mid,high-mid+1);
}
int main(void)
{
long i, n;
while(scanf("%ld", &n) != EOF && n > 0) {
a = malloc(sizeof(*a) * n);
aa = malloc(sizeof(*a) * n);
for (i = 0; i < n; i++)
scanf("%lld", &a[i]);
printf("%lld\n", inversions(0, n));
free(a);
free(aa);
}
return 0;
}
int main()
{
printf("Asf");
FILE *fp;
int nums[100000];
int nums_index=0;
fp = fopen("/home/vamshi/int.txt","r");
int i;
int temp_num[10];
int temp_index=0;
int a;
while((a = (int)getc(fp))!=EOF)
{
if(a==13)
{
int num = 0;
for(i=0;i<temp_index;i++)
{
num = num + (temp_num[i]* pow(10,temp_index-i-1));
}
nums[nums_index++] = num;
temp_index = 0;
a = (int)getc(fp);
}
else
{
temp_num[temp_index++] = a-48;
}
}
int num = 0;
for(i=0;i<temp_index;i++)
{
num = num + (temp_num[i]* pow(10,temp_index-i-1));
}
nums[nums_index++] = num;
printf("Started.......!");
printf("ld",inversions(nums,100000));
return 1;
}
int main() {
int t;
scanf("%d\n",&t);
while(t--)
{
int n;
scanf("%d\n",&n);
long int *arr=(long int*)malloc(sizeof(long int)*n);
for(int i=0;i<n;i++)
scanf("%ld\n",&arr[i]);
printf("%ld\n",inversions(arr,n-1));
free(arr);
}
return 0;
}
int main() {
{
vector<int> t = {4, 6, 1, 2, 3, 9, 11, 7, 8, 101, 33, 22, 121, 24, 4};
EXPECT_EQ(inversionsNaive(t), inversions(t));
}
}
