51NOD 1962 区间计数 单调栈+二分 / 线段树+扫描线

#include <bits/stdc++.h>
inline long long read(){long long x=0,f=1;char ch=getchar();while(ch<‘0‘||ch>‘9‘){if(ch==‘-‘)f=-1;ch=getchar();}while(ch>=‘0‘&&ch<=‘9‘){x=x*10+ch-‘0‘;ch=getchar();}return x*f;}
using namespace std;
#define ls i<<1
#define rs ls | 1
#define mid ((ll+rr)>>1)
#define MP make_pair
typedef long long LL;
typedef unsigned long long ULL;
const long long INF = 1e18+1LL;
const double pi = acos(-1.0);
const int  N = 4e5 + 10, M = 1e3, inf = 2e9;

int n,a[N],b[N];
int l[2],r[2],q[2][N],pos[2][N];
LL cal(int x,int p,int i) {
     int ll = l[p], rr = r[p],ok = ll;
     while(ll <= rr) {
        if(q[p][mid] > x) {
            ll = mid + 1;
        } else ok = mid,rr = mid - 1;
    }
  //  cout<<i<<" "<<p<<" "<<ok<<" "<<q[p][ok]<<" "<<x<<endl;
    int mmp1,mmp2;
    mmp1 = max(pos[p][ok-1]+1,pos[p^1][r[p^1]-1]+1);
    mmp2 = i-1;

    if(q[p][ok] == x)
        return 1LL * max(min(pos[p^1][r[p^1]],pos[p][ok]) - mmp1+1,0)
        * max(mmp2 - max(pos[p^1][r[p^1]],pos[p][ok]) + 1,0);
    else return 0;
}
int main() {
    cin >> n;
    for(int i = 1; i <= n; ++i) scanf("%d",&a[i]);
    for(int i = 1; i <= n; ++i) scanf("%d",&b[i]);
    l[0] = l[1] = 1;
    r[0] = r[1] = 0;
    pos[0][0] = pos[1][0] = 0;
    LL ans = 0;
    for(int i = 1; i <= n; ++i) {
        LL ret = 0;
        while(l[0] <= r[0] && a[i] >= q[0][r[0]]) {
            ret += cal(q[0][r[0]],1,i);
            r[0]--;
        }
        q[0][++r[0]] = a[i];pos[0][r[0]] = i;
        while(l[1] <= r[1] && b[i] >= q[1][r[1]]) {
            ret += cal(q[1][r[1]],0,i);
            r[1]--;
        }
        q[1][++r[1]] = b[i];pos[1][r[1]] = i;
        //cout<<"fuck "<<i<<" "  << ret<<endl;
        ans += ret;
    }
    while(l[0] <= r[0]) {
        ans += cal(q[0][r[0]],1,n+1);
        r[0]--;
    }
    cout<<ans<<endl;
    return 0;
}