单调栈题目总结

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<queue>
using namespace std;
const int M=50007;
int read(){
    int ans=0,f=1,c=getchar();
    while(c<‘0‘||c>‘9‘){if(c==‘-‘) f=-1; c=getchar();}
    while(c>=‘0‘&&c<=‘9‘){ans=ans*10+(c-‘0‘); c=getchar();}
    return ans*f;
}
int n,h[M],v[M];
int st[M],top,s[M],ans;
int main()
{
    n=read();
    for(int i=1;i<=n;i++) h[i]=read(),v[i]=read();
    for(int i=1;i<=n;i++){
        while(top&&h[st[top]]<h[i]) s[i]+=v[st[top--]];
        st[++top]=i;
    }
    top=0;
    for(int i=n;i;i--){
        while(top&&h[st[top]]<h[i]) s[i]+=v[st[top--]];
        st[++top]=i;
    }
    for(int i=1;i<=n;i++) ans=max(ans,s[i]);
    printf("%d\n",ans);
    return 0;
}

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<queue>
#define LL long long
using namespace std;
const int M=1e5+7;
int read(){
    int ans=0,f=1,c=getchar();
    while(c<‘0‘||c>‘9‘){if(c==‘-‘) f=-1; c=getchar();}
    while(c>=‘0‘&&c<=‘9‘){ans=ans*10+(c-‘0‘); c=getchar();}
    return ans*f;
}
int h[M],n;
LL ans;
int st[M],top;
int main()
{
    n=read();
    for(int i=1;i<=n;i++) h[i]=read();
    for(int i=1;i<=n;i++){
        while(top&&h[st[top]]<=h[i]) top--;
        ans+=top; st[++top]=i;
    }printf("%lld\n",ans);
    return 0;
}