b98fbebb35 2011-09-14        kinaba: #include <iostream>
b98fbebb35 2011-09-14        kinaba: #include <sstream>
b98fbebb35 2011-09-14        kinaba: #include <iomanip>
b98fbebb35 2011-09-14        kinaba: #include <vector>
b98fbebb35 2011-09-14        kinaba: #include <string>
b98fbebb35 2011-09-14        kinaba: #include <map>
b98fbebb35 2011-09-14        kinaba: #include <set>
b98fbebb35 2011-09-14        kinaba: #include <algorithm>
b98fbebb35 2011-09-14        kinaba: #include <numeric>
b98fbebb35 2011-09-14        kinaba: #include <iterator>
b98fbebb35 2011-09-14        kinaba: #include <functional>
b98fbebb35 2011-09-14        kinaba: #include <complex>
b98fbebb35 2011-09-14        kinaba: #include <queue>
b98fbebb35 2011-09-14        kinaba: #include <stack>
b98fbebb35 2011-09-14        kinaba: #include <cmath>
b98fbebb35 2011-09-14        kinaba: #include <cassert>
b98fbebb35 2011-09-14        kinaba: #include <cstring>
b98fbebb35 2011-09-14        kinaba: using namespace std;
b98fbebb35 2011-09-14        kinaba: typedef long long LL;
b98fbebb35 2011-09-14        kinaba: typedef complex<double> CMP;
b98fbebb35 2011-09-14        kinaba: 
b98fbebb35 2011-09-14        kinaba: static const LL MODVAL = 1000000007;
b98fbebb35 2011-09-14        kinaba: class AdjacentSwaps { public:
b98fbebb35 2011-09-14        kinaba: 	int theCount(vector <int> p)
b98fbebb35 2011-09-14        kinaba: 	{
b98fbebb35 2011-09-14        kinaba: 		int N = p.size();
b98fbebb35 2011-09-14        kinaba: 
b98fbebb35 2011-09-14        kinaba: 		vector< set<int> > child(N-1);
b98fbebb35 2011-09-14        kinaba: 		for(int s=0; s<N; ++s)
b98fbebb35 2011-09-14        kinaba: 		{
b98fbebb35 2011-09-14        kinaba: 			int e = find(p.begin(), p.end(), s) - p.begin();
b98fbebb35 2011-09-14        kinaba: 			if( s < e ) {
b98fbebb35 2011-09-14        kinaba: 				// s-1 <-- s --> s+1 --> ... --> e-1 <-- e
b98fbebb35 2011-09-14        kinaba: 				if(s-1>=0) child[s].insert(s-1);
b98fbebb35 2011-09-14        kinaba: 				for(int i=s; i+1<=e-1; ++i) child[i].insert(i+1);
b98fbebb35 2011-09-14        kinaba: 				if(e<N-1) child[e].insert(e-1);
b98fbebb35 2011-09-14        kinaba: 			}
b98fbebb35 2011-09-14        kinaba: 			else if( s > e ) {
b98fbebb35 2011-09-14        kinaba: 				// e-1 --> e <-- e+1 <-- ... <-- s-1 --> s
b98fbebb35 2011-09-14        kinaba: 				if(e-1>=0) child[e-1].insert(e);
b98fbebb35 2011-09-14        kinaba: 				for(int i=e; i+1<=s-1; ++i) child[i+1].insert(i);
b98fbebb35 2011-09-14        kinaba: 				if(s<N-1) child[s-1].insert(s);
b98fbebb35 2011-09-14        kinaba: 			}
b98fbebb35 2011-09-14        kinaba: 			else // s == e
b98fbebb35 2011-09-14        kinaba: 				return 0;
b98fbebb35 2011-09-14        kinaba: 		}
b98fbebb35 2011-09-14        kinaba: 
b98fbebb35 2011-09-14        kinaba: 		// cycle
b98fbebb35 2011-09-14        kinaba: 		N--;
b98fbebb35 2011-09-14        kinaba: 		for(int i=0; i+1<N; ++i)
b98fbebb35 2011-09-14        kinaba: 			if( child[i].count(i+1) && child[i+1].count(i) )
b98fbebb35 2011-09-14        kinaba: 				return 0;
b98fbebb35 2011-09-14        kinaba: 
b98fbebb35 2011-09-14        kinaba: 		vector<int> q(N-1);
b98fbebb35 2011-09-14        kinaba: 		for(int i=0; i+1<N; ++i) {
b98fbebb35 2011-09-14        kinaba: 			if( child[i].count(i+1) )
b98fbebb35 2011-09-14        kinaba: 				q[i] = +1;
b98fbebb35 2011-09-14        kinaba: 			else
b98fbebb35 2011-09-14        kinaba: 				q[i] = -1;
b98fbebb35 2011-09-14        kinaba: 		}
b98fbebb35 2011-09-14        kinaba: 
b98fbebb35 2011-09-14        kinaba: 		LL sum = 0;
b98fbebb35 2011-09-14        kinaba: 		for(int i=0; i<N; ++i)
b98fbebb35 2011-09-14        kinaba: 			sum += rec(q, 0, i, N-i-1);
b98fbebb35 2011-09-14        kinaba: 		return int(sum % MODVAL);
b98fbebb35 2011-09-14        kinaba: 	}
b98fbebb35 2011-09-14        kinaba: 
b98fbebb35 2011-09-14        kinaba: 	map<pair<int,int>, LL> memo;
b98fbebb35 2011-09-14        kinaba: 	LL rec(const vector<int>& q, int i, int x, int y)
b98fbebb35 2011-09-14        kinaba: 	{
b98fbebb35 2011-09-14        kinaba: 		if( i == q.size() )
b98fbebb35 2011-09-14        kinaba: 			return 1;
b98fbebb35 2011-09-14        kinaba: 		pair<int,int> key(i,x);
b98fbebb35 2011-09-14        kinaba: 		if( memo.count(key) )
b98fbebb35 2011-09-14        kinaba: 			return memo[key];
b98fbebb35 2011-09-14        kinaba: 
b98fbebb35 2011-09-14        kinaba: 		if( q[i] == -1 ) {
b98fbebb35 2011-09-14        kinaba: 			LL sum = 0;
b98fbebb35 2011-09-14        kinaba: 			for(int k=0; k<x; ++k)
b98fbebb35 2011-09-14        kinaba: 				sum += rec(q, i+1, k, y+(x-k-1));
b98fbebb35 2011-09-14        kinaba: 			return memo[key] = sum % MODVAL;
b98fbebb35 2011-09-14        kinaba: 		} else {
b98fbebb35 2011-09-14        kinaba: 			LL sum = 0;
b98fbebb35 2011-09-14        kinaba: 			for(int k=0; k<y; ++k)
b98fbebb35 2011-09-14        kinaba: 				sum += rec(q, i+1, x+k, y-k-1);
b98fbebb35 2011-09-14        kinaba: 			return memo[key] = sum % MODVAL;
b98fbebb35 2011-09-14        kinaba: 		}
b98fbebb35 2011-09-14        kinaba: 	}
b98fbebb35 2011-09-14        kinaba: };
b98fbebb35 2011-09-14        kinaba: 
b98fbebb35 2011-09-14        kinaba: // BEGIN CUT HERE
b98fbebb35 2011-09-14        kinaba: #include <ctime>
b98fbebb35 2011-09-14        kinaba: double start_time; string timer()
b98fbebb35 2011-09-14        kinaba:  { ostringstream os; os << " (" << int((clock()-start_time)/CLOCKS_PER_SEC*1000) << " msec)"; return os.str(); }
b98fbebb35 2011-09-14        kinaba: template<typename T> ostream& operator<<(ostream& os, const vector<T>& v)
b98fbebb35 2011-09-14        kinaba:  { os << "{ ";
b98fbebb35 2011-09-14        kinaba:    for(typename vector<T>::const_iterator it=v.begin(); it!=v.end(); ++it)
b98fbebb35 2011-09-14        kinaba:    os << '\"' << *it << '\"' << (it+1==v.end() ? "" : ", "); os << " }"; return os; }
b98fbebb35 2011-09-14        kinaba: void verify_case(const int& Expected, const int& Received) {
b98fbebb35 2011-09-14        kinaba:  bool ok = (Expected == Received);
b98fbebb35 2011-09-14        kinaba:  if(ok) cerr << "PASSED" << timer() << endl;  else { cerr << "FAILED" << timer() << endl;
b98fbebb35 2011-09-14        kinaba:  cerr << "\to: \"" << Expected << '\"' << endl << "\tx: \"" << Received << '\"' << endl; } }
b98fbebb35 2011-09-14        kinaba: #define CASE(N) {cerr << "Test Case #" << N << "..." << flush; start_time=clock();
b98fbebb35 2011-09-14        kinaba: #define END	 verify_case(_, AdjacentSwaps().theCount(p));}
b98fbebb35 2011-09-14        kinaba: int main(){
b98fbebb35 2011-09-14        kinaba: 
b98fbebb35 2011-09-14        kinaba: CASE(0)
b98fbebb35 2011-09-14        kinaba: 	int p_[] = {1, 2, 0};
b98fbebb35 2011-09-14        kinaba: 	  vector <int> p(p_, p_+sizeof(p_)/sizeof(*p_));
b98fbebb35 2011-09-14        kinaba: 	int _ = 1;
b98fbebb35 2011-09-14        kinaba: END
b98fbebb35 2011-09-14        kinaba: CASE(1)
b98fbebb35 2011-09-14        kinaba: 	int p_[] = {0, 1};
b98fbebb35 2011-09-14        kinaba: 	  vector <int> p(p_, p_+sizeof(p_)/sizeof(*p_));
b98fbebb35 2011-09-14        kinaba: 	int _ = 0;
b98fbebb35 2011-09-14        kinaba: END
b98fbebb35 2011-09-14        kinaba: CASE(2)
b98fbebb35 2011-09-14        kinaba: 	int p_[] = {2, 0, 3, 1};
b98fbebb35 2011-09-14        kinaba: 	  vector <int> p(p_, p_+sizeof(p_)/sizeof(*p_));
b98fbebb35 2011-09-14        kinaba: 	int _ = 2;
b98fbebb35 2011-09-14        kinaba: END
b98fbebb35 2011-09-14        kinaba: CASE(3)
b98fbebb35 2011-09-14        kinaba: 	int p_[] = {1, 0, 3, 2};
b98fbebb35 2011-09-14        kinaba: 	  vector <int> p(p_, p_+sizeof(p_)/sizeof(*p_));
b98fbebb35 2011-09-14        kinaba: 	int _ = 0;
b98fbebb35 2011-09-14        kinaba: END
b98fbebb35 2011-09-14        kinaba: CASE(4)
b98fbebb35 2011-09-14        kinaba: 	int p_[] = {1, 3, 0, 5, 2, 7, 4, 8, 10, 6, 12, 9, 14, 11, 16, 13, 18, 15, 19, 17};
b98fbebb35 2011-09-14        kinaba: 	  vector <int> p(p_, p_+sizeof(p_)/sizeof(*p_));
b98fbebb35 2011-09-14        kinaba: 	int _ = 716743312;
b98fbebb35 2011-09-14        kinaba: END
b98fbebb35 2011-09-14        kinaba: /*
b98fbebb35 2011-09-14        kinaba: CASE(5)
b98fbebb35 2011-09-14        kinaba: 	int p_[] = ;
b98fbebb35 2011-09-14        kinaba: 	  vector <int> p(p_, p_+sizeof(p_)/sizeof(*p_));
b98fbebb35 2011-09-14        kinaba: 	int _ = ;
b98fbebb35 2011-09-14        kinaba: END
b98fbebb35 2011-09-14        kinaba: CASE(6)
b98fbebb35 2011-09-14        kinaba: 	int p_[] = ;
b98fbebb35 2011-09-14        kinaba: 	  vector <int> p(p_, p_+sizeof(p_)/sizeof(*p_));
b98fbebb35 2011-09-14        kinaba: 	int _ = ;
b98fbebb35 2011-09-14        kinaba: END
b98fbebb35 2011-09-14        kinaba: */
b98fbebb35 2011-09-14        kinaba: }
b98fbebb35 2011-09-14        kinaba: // END CUT HERE