​​https://www.51nod.com/Challenge/Problem.html#!#problemId=1810​​

和蓝桥上一道题一模一样 但是卡线段树

官方题解

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int maxn=1e6+10;

int ary[maxn],minn[maxn],maxx[maxn],book[3*maxn];
int n;

ll solve(int l,int r)
{
    ll res;
    int i,m,p,q,tmp;
    if(l==r) return 1;
    m=(l+r)/2;
    res=solve(l,m)+solve(m+1,r);

    minn[m]=maxx[m]=ary[m];
    for(i=m-1;i>=l;i--){
        minn[i]=min(minn[i+1],ary[i]);
        maxx[i]=max(maxx[i+1],ary[i]);
    }
    minn[m+1]=maxx[m+1]=ary[m+1];
    for(i=m+2;i<=r;i++){
        minn[i]=min(minn[i-1],ary[i]);
        maxx[i]=max(maxx[i-1],ary[i]);
    }

    for(i=m;i>=l;i--){
        tmp=i+maxx[i]-minn[i];
        if(m+1<=tmp&&tmp<=r&&minn[i]<minn[tmp]&&maxx[tmp]<maxx[i]) res++;
    }

    for(i=m+1;i<=r;i++){
        tmp=i-maxx[i]+minn[i];
        if(l<=tmp&&tmp<=m&&minn[i]<minn[tmp]&&maxx[tmp]<maxx[i]) res++;
    }

    p=m+1,q=m+1;
    for(i=m;i>=l;i--){
        while(q<=r&&maxx[q]<maxx[i]) book[minn[q]+q+1000000]++,q++;
        while(p<q&&minn[p]>minn[i]) book[minn[p]+p+1000000]--,p++;
        res+=(ll)(book[maxx[i]+i+1000000]);
    }
    while(p<q) book[minn[p]+p+1000000]--,p++;

    p=m,q=m;
    for(i=m+1;i<=r;i++){
        while(q>=l&&maxx[q]<maxx[i]) book[minn[q]-q+1000000]++,q--;
        while(p>q&&minn[p]>minn[i]) book[minn[p]-p+1000000]--,p--;
        res+=(ll)(book[maxx[i]-i+1000000]);
    }
    while(p>q) book[minn[p]-p+1000000]--,p--;

    return res;
}

int main()
{
    int i;
    scanf("%d",&n);
    for(i=1;i<=n;i++) scanf("%d",&ary[i]);
    printf("%lld\n",solve(1,n));
    return 0;
}