POJ 3264 Balanced Lineup

求区间最大值减去最小值的值，用线段树再好不过了，这里线段树的功能就是查询区间

的最大值和最小值，没有单点更新。

#include<cstdio>

#include<algorithm>

using namespace std;



#define lson l, m, rt << 1

#define rson m + 1, r, rt << 1 | 1



const int MAXN = 500107;

int Max[MAXN << 2], Min[MAXN << 2];

int N, Q;



void PushUp( int rt)

{

    Max[rt] = max( Max[rt << 1], Max[rt << 1 | 1]);

    Min[rt] = min( Min[rt << 1], Min[rt << 1 | 1]);

}



void build( int l, int r, int rt)

{

    int x, m = (l + r) >> 1;

    if( l == r)

    {

        scanf( "%d", &x);

        Max[rt] = x;

        Min[rt] = x;

        return;

    }

    build(lson);

    build(rson);

    PushUp(rt);

}



int queryMax(int L, int R, int l, int r, int rt)

{

    int ret = 0, m = (l + r) >> 1;

    if( L <= l && r <= R)

    {

        return Max[rt];

    }

    if( L <= m) ret = max( ret, queryMax( L, R, lson) );

    if( R > m) ret = max( ret, queryMax(L, R, rson) );

    return ret;

}



int queryMin(int L, int R, int l, int r, int rt)

{

    int ret = 1 << 30, m = (l + r) >> 1;

    if( L <= l && r <= R)

    {

        return Min[rt];

    }

    if( L <= m) ret = min( ret, queryMin(L, R, lson));

    if( R > m) ret = min( ret , queryMin(L, R, rson));

    return ret;

}



int main()

{

    int L, R, s, t;

    while( scanf( "%d%d", &N, &Q) == 2)

    {

        build( 1, N, 1);

        while( Q --)

        {

            scanf( "%d%d", &L, &R);

            s = queryMin(L, R, 1, N, 1);

            t = queryMax(L, R, 1, N, 1);

            printf( "%d\n", t - s);

        }

    }

    return 0;

}