poj3264（线段树求区间最大最小值）

题目链接:poj3264

简单题，求区间最大值和最小值

#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
#define N 1000010
int n,a
;
int ans_x, ans_y;
struct node
{
int r,l;
int maxx,minn;
}s[N<<2];
void build(int l, int r, int n)
{
s
.l = l;
s
.r = r;
s
.maxx = 0;
s
.minn = N;
if(l == r)
{
s
.maxx = s
.minn = a[l];
return;
}
int mid = (l + r) >> 1;
build(l, mid, n<<1);
build(mid + 1, r, n<<1|1);
s
.maxx = max(s[n<<1].maxx, s[n<<1|1].maxx);
s
.minn = min(s[n<<1].minn, s[n<<1|1].minn);
}
void query(int l, int r, int n)
{
if(s
.l == l && s
.r == r)
{
ans_x = max(ans_x, s
.maxx);
ans_y = min(ans_y, s
.minn);
return;
}
int mid = (s
.l + s
.r) >> 1;
if(r <= mid)
query(l, r, n<<1);
else if(l > mid)
query(l, r, n<<1|1);
else
{
query(l, mid, n<<1);
query(mid+1, r, n<<1|1);
}
}
int main()
{
int m,t,i,x,y;
while(~scanf("%d%d",&m,&t))
{
for(i = 1; i <= m; i ++)
scanf("%d",&a[i]);
build(1,m,1);
while(t--)
{
scanf("%d%d",&x,&y);
ans_x = 0;
ans_y = N;
query(x,y,1);
printf("%d\n",ans_x-ans_y);
}
}
return 0;
}