POJ_3264 Balanced Lineup(线段树练手题)

　　用线段树水过，3s多。。。不说了，上代码：

#include <stdio.h>
#define inf 0x7fffffff
#define N 50010
struct node
{
    int l, r;
    int min, max;
}node[N*4];

int num[N], nmax, nmin;
void creat(int t, int l, int r)
{
    node[t].l = l;
    node[t].r = r;
    node[t].min = inf;
    node[t].max = -inf;
    if(l == r - 1)
    {
        if(num[l] > num[r])
        {
            node[t].min = num[r];
            node[t].max = num[l];
        }
        else
        {
            node[t].min = num[l];
            node[t].max = num[r];
        }
        return;
    }
    int mid = (l + r) >> 1;
    creat(t << 1, l, mid);
    creat(t << 1 | 1, mid , r);
    node[t].min = node[t << 1].min < node[t << 1 | 1].min ? node[t << 1].min : node[t << 1 | 1].min;
    node[t].max = node[t << 1].max > node[t << 1 | 1].max ? node[t << 1].max : node[t << 1 | 1].max;
}
void query(int t, int l, int r)
{
    if(node[t].l >= l && node[t].r <= r)
    {
        nmax = node[t].max > nmax ? node[t].max : nmax;
        nmin = node[t].min < nmin ? node[t].min : nmin;
        return ;
    }
    if(node[t].l == node[t].r - 1)    return;
    int mid = (node[t].l + node[t].r) >> 1;
    if(l >= mid)
        query(t << 1 | 1, l, r);
    else if(r <= mid)
        query(t << 1, l, r);
    else
    {
        query(t << 1, l, mid);
        query(t << 1 | 1, mid, r);
    }
}
int main()
{
    int n, q, i;
    //freopen("data.in", "r", stdin);
    scanf("%d%d", &n, &q);
    for(i = 1; i <= n; i++)
        scanf("%d", &num[i]);
    creat(1, 1, n);
    while(q--)
    {
        int x, y;
        scanf("%d%d", &x, &y);
        if(x == y)
        {
            printf("0\n");
            continue;
        }
        nmax = -inf; nmin = inf;
        query(1, x, y);
        printf("%d\n", nmax - nmin);
    }
    return 0;
}