32 mint FAC(LL n) { while( FAC_.size()<=n ) FAC_.push_back( FAC_.back()*FAC_.size() 32 mint FAC(LL n) { while( FAC_.size()<=n ) FAC_.push_back( FAC_.back()*FAC_.size() 33 33 34 // nCk :: O(log MODVAL) time, O(n) space. 34 // nCk :: O(log MODVAL) time, O(n) space. 35 mint C(LL n, LL k) { return k<0 || n<k ? 0 : FAC(n) / (FAC(k) * FAC(n-k)); } 35 mint C(LL n, LL k) { return k<0 || n<k ? 0 : FAC(n) / (FAC(k) * FAC(n-k)); } 36 36 37 // nCk :: O(1) time, O(n^2) space. 37 // nCk :: O(1) time, O(n^2) space. 38 vector< vector<mint> > CP_; 38 vector< vector<mint> > CP_; 39 mint C(LL n, LL k) { | 39 mint C(int n, int k) { 40 while( CP_.size() <= n ) { 40 while( CP_.size() <= n ) { 41 int nn = CP_.size(); 41 int nn = CP_.size(); 42 CP_.push_back(vector<mint>(nn+1,1)); 42 CP_.push_back(vector<mint>(nn+1,1)); 43 for(int kk=1; kk<nn; ++kk) 43 for(int kk=1; kk<nn; ++kk) 44 CP_[nn][kk] = CP_[nn-1][kk-1] + CP_[nn-1][kk]; 44 CP_[nn][kk] = CP_[nn-1][kk-1] + CP_[nn-1][kk]; 45 } 45 } 46 return k<0 || n<k ? 0 : CP_[n][k]; 46 return k<0 || n<k ? 0 : CP_[n][k];