BZOJ 1303 中位数图

#include<iostream>
#include<cstdio>
#include<cstring>
#include<cmath>
#define maxn 100500
using namespace std;
long long n,a[maxn],mx[maxn],mi[maxn],cnta[maxn][3],cntb[maxn][3],regis[4],b,rec;
long long num[maxn],kk=0,ans=0;
long long vv(long long x)
{
    if (x<0) return -x;
    return x;
}
int main()
{
    scanf("%lld%lld",&n,&b);
    for (long long i=1;i<=n;i++)
    {
        scanf("%lld",&a[i]);
        if (a[i]>b) {mx[i]=mx[i-1]+1;mi[i]=mi[i-1];}
        else if (a[i]<b) {mx[i]=mx[i-1];mi[i]=mi[i-1]+1;}
        else {rec=i;mx[i]=mx[i-1];mi[i]=mi[i-1];}
    }
    for (long long i=1;i<=n;i++)
    {
        if (i<=rec-1)
        {
            num[i]=(mx[rec-1]-mx[i-1])-(mi[rec]-mi[i-1]);
            if (vv(num[i])>kk) kk=vv(num[i]);
        }
        else if (i>=rec+1)
        {
            num[i]=(mx[i]-mx[rec])-(mi[i]-mi[rec]);
            if (vv(num[i])>kk) kk=vv(num[i]);
        }
    }    
    for (long long i=1;i<=rec-1;i++)
    {
        if (num[i]<0) cntb[-num[i]][1]++;
        else if (num[i]>0) cnta[num[i]][1]++;
        else regis[1]++;
    }
    for (long long i=rec+1;i<=n;i++)
    {
        if (num[i]<0) cntb[-num[i]][2]++;
        else if (num[i]>0) cnta[num[i]][2]++;
        else regis[2]++;
    }
    for (long long i=1;i<=kk;i++)
    {
        ans+=cnta[i][1]*cntb[i][2];
        ans+=cntb[i][1]*cnta[i][2];
    }
    ans=ans+regis[1]*regis[2]+regis[1]+regis[2]+1;
    printf("%lld\n",ans);
    return 0;
}