单调栈【直方图】【acwing】

https://blog.csdn.net/qq_43109145/article/details/89522309

#include
#include
#include
using namespace std;
typedef long long  ll;
const int N=100010;
int n;
int h[N],q[N],l[N],r[N];
stack s1,s2,s3;


int main(){
    while(cin>>n&&n){
        
        for(int i=1;i<=n;i++){
            cin>>h[i];
        }
        {
            s1=s3;
            for(int i=1;i<=n;i++){
                while(!s1.empty() && h[i]<=h[s1.top()]) s1.pop();
                if(!s1.empty()) l[i]=s1.top();
                else l[i]=0;
                s1.push(i);
            }
        }


        {
            s2=s3;
            for(int i=n;i>=1;i--){
                while(!s2.empty() && h[s2.top()]>=h[i]) s2.pop();;
                if(!s2.empty()) r[i]=s2.top();
                else r[i]=n+1;
                s2.push(i);
            }
        }

        ll res=0;
        for(int i=1;i<=n;i++){
            res=max(res,h[i]*(r[i]-l[i]-1ll));
        }
        cout<