POJ 3264 Balanced Lineup（线段树 区间最值）

 1 //POJ 3264 Balanced Lineup
 2 //区间最值 
 3 #include <cstdio>
 4 #include <iostream>
 5 #include <algorithm>
 6 using namespace std;
 7 
 8 typedef long long LL;
 9 const int N=50000+10;
10 const int INF=0x3f3f3f3f;
11 LL ans1,ans2,n,m;
12 
13 struct Tree
14 {
15     LL l,r;
16     LL MAX,MIN;
17 };
18 Tree tree[4*N];
19 
20 void pushup(LL x) //向上更新 
21 {
22     LL tmp=x<<1;
23     tree[x].MAX=max(tree[tmp].MAX,tree[tmp+1].MAX);
24     tree[x].MIN=min(tree[tmp].MIN,tree[tmp+1].MIN);
25 }
26 
27 void build(LL l,LL r,LL x)
28 {
29     tree[x].l=l;
30     tree[x].r=r;
31     if(l==r)
32     {
33         scanf("%lld",&tree[x].MAX);
34         tree[x].MIN=tree[x].MAX;
35         return ;
36     }    
37     LL tmp=x<<1;
38     LL mid=(l+r)>>1;
39     build(l,mid,tmp);
40     build(mid+1,r,tmp+1);
41     pushup(x);
42 }
43 
44 void query(LL l,LL r,LL x)
45 {
46     if(r<tree[x].l||l>tree[x].r) return ;
47     if(l<=tree[x].l&&r>=tree[x].r)
48     {
49         ans1=max(ans1,tree[x].MAX);
50         ans2=min(ans2,tree[x].MIN);
51         return ;
52     }    
53     LL tmp=x<<1;
54     LL mid=(tree[x].l+tree[x].r)>>1;
55     if(r<=mid) query(l,r,tmp);
56     else if(l>mid) query(l,r,tmp+1);
57     else
58     {
59         query(l,mid,tmp);
60         query(mid+1,r,tmp+1);    
61     }
62 }
63 
64 int main(){
65     LL A,B;
66     scanf("%lld%lld",&n,&m);
67     build(1,n,1);
68     for(int i=1;i<=m;i++){
69         ans1=0;ans2=INF;
70         scanf("%lld%lld",&A,&B);
71         query(A,B,1);
72         printf("%lld\n",ans1-ans2);
73     }
74     return 0;
75 }