poj 3264 -- Balanced Lineup (区间最值，线段树/RMQ）

第一次RMQ ，还好

RMQ版：

# include <cstdio># include <iostream># include <set># include <map># include <vector># include <list># include <queue># include <stack># include <cstring># include <string># include <cstdlib># include <cmath># include <algorithm>using namespace std ;const int maxn = 51000 ;int dp1 [ 20 ] [ maxn ] ;int dp2 [ 20 ] [ maxn ] ;                //小的放前面效率高不少int a [ 51000 ] ;int n ;void getdp ( ){    for ( int i = 1 ; i <= n ; i ++ )    {        dp1 [ 0 ] [ i ] = dp2 [ 0 ] [ i ] = a [ i ] ;    }    int len = floor ( log2 ( 51000 ) ) ;       //C++没有log2，取自然对数算    for ( int j = 1 ; j <= len ; j ++ )        for ( int i = 1 ; i + ( 1 << j ) - 1 <= n ; i ++ )        {            dp1 [ j ] [ i ] = min ( dp1 [ j - 1 ] [ i ] , dp1 [ j - 1 ] [ i + (1 << (j - 1)) ] ) ;            dp2 [ j ] [ i ] = max ( dp2 [ j - 1 ] [ i ] , dp2 [ j - 1 ] [ i + (1 << (j - 1)) ] ) ;        }}int main ( ){    int q ;    scanf ( "%d%d" , & n , & q ) ;    for ( int i = 1 ; i <= n ; i ++ )    {        scanf ( "%d" , a + i ) ;    }    getdp ( ) ;    while ( q -- )    {        int m , n ;        scanf ( "%d%d" , & m , & n ) ;        int len = floor ( log2 ( n - m + 1 ) ) ;        int maxx = max ( dp2 [ len ] [ m ] , dp2 [ len ] [ n - ( 1 << len ) + 1 ] ) ;        int minn = min ( dp1 [ len ] [ m ] , dp1 [ len ] [ n - ( 1 << len ) + 1 ] ) ;        printf ( "%d\n" , maxx - minn ) ;    }}

线段树版：

# include <cstdio># include <iostream># include <set># include <map># include <vector># include <list># include <queue># include <stack># include <cstring># include <string># include <cstdlib># include <cmath># include <algorithm>using namespace std ;const int maxn = 51000 ;const int MAX = 2100000000 ;int low , high ;struct Tree{    int maxx , minn ;} tree [ maxn * 4 ] ;void pushup ( int pos ){    tree [ pos ] . minn = min ( tree [ pos * 2 ] . minn , tree [ pos * 2 + 1 ] . minn ) ;    tree [ pos ] . maxx = max ( tree [ pos * 2 ] . maxx , tree [ pos * 2 + 1 ] . maxx ) ;}void build ( int l , int r , int pos ){    if ( l == r )    {        scanf ( "%d" , & tree [ pos ] . minn ) ;        tree [ pos ] . maxx = tree [ pos ] . minn ;        return ;    }    int m = ( l + r ) / 2 ;    build ( l , m , pos * 2 ) ;    build ( m + 1 , r , pos * 2 + 1 ) ;    pushup ( pos ) ;}void quer ( int l , int r , int pos , int L , int R ){    if ( l >= L && r <= R )    {        high = max ( high , tree [ pos ] . maxx ) ;        low = min ( low , tree [ pos ] . minn ) ;        return ;    }    int m = ( l + r ) / 2 ;    if ( m >= L )        quer ( l , m , pos * 2 , L , R ) ;    if ( m + 1 <= R )        quer ( m + 1 , r , pos * 2 + 1 , L , R ) ;}int main ( ){    int n , q ;    scanf ( "%d%d" , & n , & q ) ;    build ( 1 , n , 1 ) ;    while ( q -- )    {        int L , R ;        scanf ( "%d%d" , & L , & R ) ;        high = 0 , low = MAX ;        quer ( 1 , n , 1 , L , R ) ;        printf ( "%d\n" , high - low ) ;    }}