BZOJ1303(CQOI2009)[中位数图]--奇技淫巧

#include<cstdio>
#include<cstring>
#define LL long long
using namespace std;
const int maxn=200005,tt=100000;
int n,m,where,num[maxn],sum[maxn];
LL ans;
inline char nc()
{
static char buf[100000],*l,*r;
if (l==r) r=(l=buf)+fread(buf,1,100000,stdin);
if (l==r) return EOF; return *l++;
}
inline int Read()
{
int res=0,f=1; char ch=nc(),cc=ch;
while (ch<'0'||ch>'9') cc=ch,ch=nc();
if (cc=='-') f=-1;
while (ch>='0'&&ch<='9') res=res*10+ch-48,ch=nc();
return res*f;
}
int main()
{
freopen("1303.in","r",stdin);
freopen("1303.out","w",stdout);
n=Read(); m=Read(); sum[0]=where=ans=0;
memset(num,0,sizeof(num)); num[tt]++;
for (int i=1; i<=n; i++)
{
int x=Read(),p=0;
if (x>m) p=1;
if (x<m) p=-1;
if (x==m) where=i;
sum[i]=sum[i-1]+p;
if (!where) num[sum[i]+tt]++;
}
for (int i=where; i<=n; i++) ans+=num[sum[i]+tt];
printf("%lld",ans);
return 0;
}