luogu P1966 火柴排队
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/* luogu P1966 火柴排队 神TM逆序对。。。 noip怎么这么坑啊。。 暴力都没得打 此题模拟考试时爆了0 做法 将A数组排序,由于B数组与A数组是一一对应的 那么B数组的位置也会发生相应的变化 此时B数组逆序数对数即为答案 */ #include <cstdio> #include <iostream> #include <algorithm> const int BUF = 123123123; char Buf[BUF], *buf = Buf; inline void read (int &now) { for (now = 0; !isdigit (*buf); ++ buf); for (; isdigit (*buf); now = now * 10 + *buf - ‘0‘, ++ buf); } #define Mod 99999997 #define Max 1232334 struct Data { int x, Id; bool operator < (const Data &now) const { return this->x < now.x; } }; Data a[Max], b[Max]; int key[Max]; struct Bit_Tree { protected : int data[Max], N; public : inline void Prepare (int x) { this->N = x; } void C (int pos) { for (; pos <= N; pos += pos & -pos) ++ data[pos]; } int Q (int pos) { register int i; int res = 0; for (i = N; i; i -= i & -i) res += data[i]; for (i = pos - 1; i; i -= i & -i) res -= data[i]; return res; } }; Bit_Tree Bit; int Main () { freopen ("match.in", "r", stdin); freopen ("match.ans", "w", stdout); fread (buf, 1, BUF, stdin); int N; read (N); register int i; int Answer = 0; for (i = 1; i <= N; ++ i) read (a[i].x), a[i].Id = i; for (i = 1; i <= N; ++ i) read (b[i].x), b[i].Id = i; std :: sort (a + 1, a + 1 + N); std :: sort (b + 1, b + 1 + N); for (i = 1; i <= N; ++ i) key[a[i].Id] = b[i].Id; for (i = 1, Bit.Prepare (N); i <= N; ++ i) { Bit.C (key[i]); Answer = (Answer + Bit.Q (key[i] + 1)) % Mod; } printf ("%d", Answer); return 0; } int ZlycerQan = Main (); int main (int argc, char *argv[]) {;}
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