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;
}