hdu 1506 Largest Rectangle in a Histogram

#include<iostream>#include<vector>#include<algorithm>#include<cstdio>#include<queue>#include<stack>#include<string>#include<map>#include<set>#include<cmath>#include<cassert>#include<cstring>#include<iomanip>using namespace std;#ifdef _WIN32#define i64 __int64#define out64 "%I64d\n"#define in64 "%I64d"#else#define i64 long long#define out64 "%lld\n"#define in64 "%lld"#endif/************ for topcoder by zz1215 *******************/#define FOR(i,a,b)      for( int i = (a) ; i <= (b) ; i ++)#define FFF(i,a)        for( int i = 0 ; i < (a) ; i ++)#define FFD(i,a,b)      for( int i = (a) ; i >= (b) ; i --)#define S64(a)          scanf(in64,&a)#define SS(a)           scanf("%d",&a)#define LL(a)           ((a)<<1)#define RR(a)           (((a)<<1)+1)#define pb              push_back#define CL(Q)           while(!Q.empty())Q.pop()#define MM(name,what)   memset(name,what,sizeof(name))#define MAX(a,b)        ((a)>(b)?(a):(b))#define MIN(a,b)        ((a)<(b)?(a):(b))#define read            freopen("in.txt","r",stdin)#define write           freopen("out.txt","w",stdout)const int inf = 0x3f3f3f3f;const i64 inf64 = 0x3f3f3f3f3f3f3f3fLL;const double oo = 10e9;const double eps = 10e-9;const double pi = acos(-1.0);const int maxn = 1000111;int n;i64 a[maxn];i64 l[maxn];int pos[maxn];int cnt;i64 ans;void gao(int now,int x){    while(a[cnt-1]>now){ans=MAX(ans,(x-l[cnt-1])*a[cnt-1]);cnt--;}l[cnt]=pos[cnt-1]+1;a[cnt]=now;pos[cnt]=x;cnt++;return ;}int main(){int now;while(cin>>n){if(!n) return 0;pos[0]=l[0]=ans=0;a[0]=-1;cnt=1;for(int i=1;i<=n;i++){SS(now);gao(now,i);}gao(-1,n+1);printf("%I64d\n",ans);}return 0;}