POJ 3278 Balanced Lineup【线段树】

 1 #include<iostream>  
 2 #include<cstdio>  
 3 #include<cstring> 
 4 #include <cmath> 
 5 #include<stack>
 6 #include<vector>
 7 #include<map> 
 8 #include<set>
 9 #include<queue> 
10 #include<algorithm>  
11 using namespace std;
12 
13 typedef long long LL;
14 const int INF = (1<<30)-1;
15 const int mod=1000000007;
16 const int maxn=1000005;
17 
18 int a[maxn];
19 int nmax,nmin;
20 
21 struct node{
22     int l,r;//记录区间的左右端点 
23     int nmax,nmin;//记录区间的最大值，最小值 
24 };
25 
26 node tree[4*maxn];
27 
28 void build_tree(int i,int l,int r){//建树 
29     tree[i].l=l;
30     tree[i].r=r;
31     if(l==r){
32         tree[i].nmin=tree[i].nmax=a[l];
33         return;        
34     }
35     int mid=(l+r)/2;
36     build_tree(2*i,l,mid);
37     build_tree(2*i+1,mid+1,r);
38     tree[i].nmin=min(tree[2*i].nmin,tree[2*i+1].nmin);
39     tree[i].nmax=max(tree[2*i].nmax,tree[2*i+1].nmax);
40 }
41 
42 void query(int i,int l,int r){//查询 
43     if(tree[i].nmin>=nmin&&tree[i].nmax<=nmax) return;
44     if(tree[i].l==l&&tree[i].r==r){
45         nmin = min(tree[i].nmin,nmin);
46         nmax = max(tree[i].nmax,nmax);
47         return;
48     }
49     int mid=(tree[i].l+tree[i].r)/2;
50     if(r<=mid) query(2*i,l,r);
51     else if(l>mid) query(2*i+1,l,r);
52     else{
53         query(2*i,l,mid);
54         query(2*i+1,mid+1,r);
55     }
56 }
57 
58 int main(){
59     int n,q;
60     while(scanf("%d %d",&n,&q)!=EOF){
61         for(int i=1;i<=n;i++) scanf("%d",&a[i]);
62         build_tree(1,1,n);
63         
64         while(q--){
65             nmin=INF;nmax=-INF;
66             int l,r;
67             scanf("%d %d",&l,&r);
68             query(1,l,r);
69             printf("%d\n",nmax-nmin);
70         }
71     }
72     return 0;
73 }