洛谷P2880 [USACO07JAN] Balanced Lineup G（树状数组/线段树）

维护区间最值的模板题。

1.树状数组

 1 #include<bits/stdc++.h>
 2 //树状数组做法
 3 using namespace std;
 4 const int N=5e4+10;
 5 int m,ma[N],mi[N],n,c[N];
 6
 7 int lowbit(int x){
 8     return x&(-x);
 9 }
10
11 void ins(int x,int v){
12     while(x<=n){
13         ma[x]=max(ma[x],v);mi[x]=min(mi[x],v);
14         x+=lowbit(x);
15     }
16 }
17
18 int que(int L,int R){
19     int maxx=-1,minn=1e9;
20     while(L<=R){
21         for(;R-lowbit(R)>=L;R-=lowbit(R)) maxx=max(maxx,ma[R]),minn=min(minn,mi[R]);
22         maxx=max(c[R],maxx);minn=min(minn,c[R]);
23         R--;
24     }
25     return maxx-minn;
26 }
27
28 int main(){
29     memset(mi,0x3f,sizeof(mi));
30     memset(ma,0,sizeof(ma));
31     scanf("%d%d",&n,&m);
32     for(int i=1;i<=n;i++){
33         int x;scanf("%d",&x);
34         ins(i,x);
35         c[i]=x;
36     }
37     while(m--){
38         int a,b;
39         scanf("%d%d",&a,&b);
40         cout<<que(a,b)<<endl;
41     }
42 }

2.线段树

 1 #include<bits/stdc++.h>
 2 //线段树做法
 3 using namespace std;
 4 const int N=5e4+10;
 5 #define lson l,mid,pos<<1
 6 #define rson mid+1,r,pos<<1|1
 7 int maxx[N<<2],minn[N<<2],MAX,MIN;
 8
 9 void up(int pos){
10     maxx[pos]=max(maxx[pos<<1],maxx[pos<<1|1]);
11     minn[pos]=min(minn[pos<<1],minn[pos<<1|1]);
12 }
13
14 void build(int l,int r,int pos){
15     if(l==r){
16         int x;scanf("%d",&x);
17         maxx[pos]=minn[pos]=x;
18         return ;
19     }
20     int mid=(l+r)>>1;
21     build(lson);build(rson);
22     up(pos);
23 }
24
25 void query(int L,int R,int l,int r,int pos){
26     if(L<=l && R>=r){
27         MAX=max(MAX,maxx[pos]);
28         MIN=min(MIN,minn[pos]);
29         return ;
30     }
31     int mid=(l+r)>>1;
32     if(L<=mid) query(L,R,lson);
33     if(R>mid) query(L,R,rson);
34 }
35
36 int main(){
37     int n,m;
38     scanf("%d%d",&n,&m);
39     build(1,n,1);
40     while(m--){
41         MAX=0,MIN=1e9;
42         int a,b;scanf("%d%d",&a,&b);
43         query(a,b,1,n,1);
44         cout<<MAX-MIN<<endl;
45     }
46     return 0;
47 }