POJ 2201（修正版）

在前一个代码中，由于在寻找一段区间的最大最小值，用朴素的搜索办法，故造成效率低下。

后来，发现有个很好的RMQ的ST算法可以解决这个问题，果断使用之，

结果AC，用时2454ms

虽然花费时间更多，但证明了我之前的想法是对的，也让我学会了一个新算法ST算法！

#include <cstdio>#include <algorithm>#include <cassert>#include <cmath>using namespace std;const int MAX = 50010;typedef struct _Node{intk;inta;intindex;}Node;typedef struct _Tree{intparent;intleft;intright;}Tree;typedef struct _SN{intleft;intright;intparent;boolisleft;}SN;Nodedata[MAX];Treetree[MAX];intrmq[MAX][32];SNstack[MAX];voidinitrmq( int n ){int len = floor( log( double(n) )/ log( 2.0 ) );int mid;for( int i = 1 ; i <= n ; ++i )rmq[i][0] = i;for( int i = 1 ; i <= len ; ++i )for( int j = 1 ; j <= n ; ++j ){rmq[j][i] = rmq[j][i-1];mid = j + ( 1 <<( i - 1 ) ) ;if( mid <= n && data[rmq[j][i-1]].a > data[rmq[mid][i-1]].a )rmq[j][i] = rmq[mid][i-1];}}intgetrmq( int left , int right ){int len = right - left + 1;int mid = floor( log( double(len) ) / log(2.0) );int mm1 = rmq[ left ][ mid ];int mm2 = rmq[ right - ( 1 << mid ) + 1 ][ mid ];if( data[mm1].a > data[mm2].a )return mm2;elsereturn mm1;}intgetmin( int left , int right ){return getrmq( left , right );//int min = left;//for( int i = left + 1 ; i <= right ; ++i )//if( data[i].a < data[min].a )//min = i ;//return min;}voidsetchild( int parent , bool isleft , int value ){if( isleft )tree[ parent ].left = value;elsetree[ parent ].right = value;}voidcreatetree( int left , int right , int parent , bool isleft ){intstacki = 0 ;stack[ stacki].left = left;stack[ stacki ].right = right;stack[ stacki ].parent = parent;stack[ stacki ].isleft = isleft;while( stacki != -1 ){left = stack[ stacki ].left ;right = stack[ stacki ].right ;parent = stack[ stacki ].parent;isleft = stack[ stacki ].isleft;stacki--;if( left > right )setchild( parent , isleft , 0 );else if( left == right ){tree[data[left].index].parent = parent;setchild( parent , isleft , data[left].index );setchild( data[left].index , true , 0 );setchild( data[left].index , false , 0 );}else{intmid = getmin( left , right );tree[ data[mid].index ].parent = parent;setchild( parent , isleft , data[mid].index );stacki++;stack[ stacki ].left = left ;stack[ stacki ].right = mid - 1;stack[ stacki ].parent = data[ mid ].index;stack[ stacki ].isleft = true;stacki++;stack[ stacki ].left = mid + 1 ;stack[ stacki ].right = right;stack[ stacki ].parent = data[ mid ].index;stack[ stacki ].isleft = false;}}}boolcmp( const Node& left , const Node & right ){return left.k < right.k ;}int main(){int n;scanf("%d",&n);for( int i = 1 ; i <= n ; ++i ){scanf("%d%d",&data[i].k , &data[i].a );data[i].index = i;}sort( &data[1] , &data[n+1] , cmp );initrmq( n );createtree( 1 , n , 0 , true );printf("YES/n");for( int i = 1 ; i <= n ; ++i )printf("%d %d %d/n",tree[i].parent , tree[i].left , tree[i].right );}