BZOJ 1636: [Usaco2007 Jan]Balanced Lineup

 1 /*Author:WNJXYK*/
 2 #include<cstdio>
 3 using namespace std;
 4 
 5 struct Btree{
 6     int left,right;
 7     int num;
 8     int max,min;
 9 }; 
10 const int Maxn=50000; 
11 Btree tree[Maxn*4+10];
12 
13 int n,q;
14 int num[Maxn+10];
15 
16 inline int remin(int a,int b){
17     if (a<b) return a;
18     return b;
19 }
20 
21 inline int remax(int a,int b){
22     if (a>b) return a;
23     return b;
24 }
25 
26 void build(int x,int left,int right){
27     tree[x].left=left;
28     tree[x].right=right;
29     if (left==right){
30         tree[x].max=tree[x].min=tree[x].num=num[left];
31     }else{
32         int mid=(left+right)/2;
33         build(x*2,left,mid);
34         build(x*2+1,mid+1,right);
35         tree[x].max=remax(tree[x*2].max,tree[x*2+1].max);
36         tree[x].min=remin(tree[x*2].min,tree[x*2+1].min);
37     }
38 }
39 
40 int queryMax(int x,int left,int right){
41     if (left<=tree[x].left && tree[x].right<=right){
42         return tree[x].max;
43     }else{
44         int res=0;
45         int mid=(tree[x].left+tree[x].right)/2;
46         if (left<=mid) res=remax(res,queryMax(x*2,left,right));
47         if (mid+1<=right) res=remax(res,queryMax(x*2+1,left,right));
48         return res;
49     }
50 }
51 
52 int queryMin(int x,int left,int right){
53     if (left<=tree[x].left && tree[x].right<=right){
54         return tree[x].min;
55     }else{
56         int res=2147483647;
57         int mid=(tree[x].left+tree[x].right)/2;
58         if (left<=mid) res=remin(res,queryMin(x*2,left,right));
59         if (mid+1<=right) res=remin(res,queryMin(x*2+1,left,right));
60         return res;
61     }
62 }
63 
64 int main(){
65     scanf("%d%d",&n,&q);
66     for (int i=1;i<=n;i++) scanf("%d",&num[i]);
67     build(1,1,n);
68     for (int i=1;i<=q;i++){
69         int left,right;
70         scanf("%d%d",&left,&right);
71         printf("%d\n",queryMax(1,left,right)-queryMin(1,left,right));    
72     }
73     return 0;
74 }