Largest Rectangle in a Histogram

来源：互联网发布：交通节能减排数据编辑：程序博客网时间：2024/05/16 11:44

/*很经典的dp题，开始不解其意，用了简单的模拟方法，超时了n次*/

#include <iostream>#define N 100005using namespace std;__int64 b[N],s;struct node {__int64 r,l,val;}a[N];int main (){//freopen("h.txt","r",stdin);int i,n;while(scanf("%d",&n),n){memset(b,0,sizeof(b));for(i=1;i<=n;i++) {scanf("%I64d",&a[i].val);a[i].l=a[i].r=i;}a[0].val=a[n+1].val=-1;for(i=1;i<=n;i++)while(a[a[i].l-1].val>=a[i].val) a[i].l=a[a[i].l-1].l;for(i=n;i>0;i--)while(a[a[i].r+1].val>=a[i].val) a[i].r=a[a[i].r+1].r;for(s=-1,i=1;i<=n;i++)s=(s<(a[i].r-a[i].l+1)*a[i].val)?(a[i].r-a[i].l+1)*a[i].val:s;printf("%I64d\n",s);}return 0;}

/*下面是超时版的，思路其实是一样的。感叹dp的优势*/

#include <iostream>#define N 100005using namespace std;__int64 a[N],b[N];int main (){//freopen("h.txt","r",stdin);int i,j,n;while(scanf("%d",&n),n){for(i=1;i<=n;i++) scanf("%I64d",&a[i]);a[0]=a[n+1]=-1;for(i=1;i<=n;i++){j=i;__int64 w=a[i];while(1<=j && a[j]>=a[i])if(a[--j]>=a[i]) w+=a[i];j=i;while(j<=n && a[j]>=a[i])if(a[++j]>=a[i]) w+=a[i];b[i]=w;}__int64 s=0;for(i=1;i<=n;i++) if(s<b[i]) s=b[i];printf("%I64d\n",s);}return 0;}