BZOJ 1303: [CQOI2009]中位数图

/*
BZOJ 1303: [CQOI2009]中位数图

对于一个数
若当前数大于中位数，则记为1
小于中位数，记为-1，等于则记为0

对原数列做一个前缀和

观察发现，若一段区间符合要求
则该段区间内大于中位数的数的数量等于小于中位数的
那么统计一下每个前缀和出现的次数就好了

*/
#include <cstdio>
#include <iostream>

const int BUF = 12312313;
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 Max 100002
int c[Max], s[Max];
short fc[Max], zc[Max];

int Main ()
{
fread (buf, 1, BUF, stdin); int N, B; read (N), read (B);
register int i, j; int x, p = -1, Answer = 0;
for (i = 1; i <= N; ++ i)
{
read (x); s[i] = s[i - 1];
if (x > B) ++ s[i];    else if (x < B) -- s[i]; else p = i;
if (p == -1) s[i] < 0 ? ++ fc[- s[i]] : ++ zc[s[i]];
}
for (++ zc[0]; p <= N; ++ p) Answer += s[p] < 0 ? fc[- s[p]] : zc[s[p]];
printf ("%d", Answer);
return 0;
}
int ZlycerQan = Main ();
int main (int argc, char *argv[]) {;}