POJ 2559

单调栈问题，跟2796差不多。

要注意的是，一次栈扫描就可以决定左右边界了。

#include <cstdio>using namespace std;constint MAX = 100010;typedef struct _Node{intdata;intleft;intright;}Node;Nodedata[MAX];intstack[MAX];intn,stacki;voidsetleftright(){stacki = 0 ;for( int i = 0 ; i != n ; ++i ){while( stacki != 0 && data[ stack[ stacki - 1 ] ].data > data[i].data )data[ stack[ --stacki ] ].right = i - 1 ;stack[stacki++] = i;if( stacki == 1 )data[i].left = 0 ;elsedata[i].left = stack[ stacki - 2 ] + 1;}while( stacki != 0 )data[ stack[--stacki] ].right = n - 1 ;}long longfind(){long longmax = -1;long longmaxmid;for( int i = 0 ; i != n ; ++i ){intmid1 = data[i].left ;intmid2 = data[i].right;maxmid = mid2 - mid1 + 1 ;maxmid *= data[i].data;if( maxmid > max )max = maxmid;}return max;}intmain(){while( scanf("%d",&n) , n != 0 ){for( int i = 0 ; i != n ; ++i )scanf("%d",&data[i].data);setleftright();printf("%lld/n",find());}return 0;}