B - I Hate It (线段树，单点更新)

 1 # include<cstdio>
 2 # include<iostream>
 3 # include<algorithm>
 4 # include<string>
 5 
 6 using namespace std;
 7 
 8 # define MAX 200004
 9 # define lid (id<<1)
10 # define rid (id<<1|1)
11 
12 
13 int a[MAX];
14 struct Segtree
15 {
16     int l,r;
17     int mx;
18 }tree[MAX*4];
19 
20 
21 void push_up( int id )
22 {
23     tree[id].mx = max(tree[lid].mx,tree[rid].mx);
24 }
25 
26 
27 void build ( int id,int l,int r )
28 {
29     tree[id].l = l; tree[id].r = r;
30     if ( l==r )
31     {
32         tree[id].mx = a[l];
33         return;
34     }
35     int mid = ( tree[id].l+tree[id].r )>>1;
36     build(lid,l,mid);
37     build(rid,mid+1,r);
38     push_up(id);
39 }
40 
41 void update( int id,int x,int val )
42 {
43     if ( tree[id].l==x&&tree[id].r==x )
44     {
45         tree[id].mx = val;
46         return;
47     }
48     int mid = ( tree[id].l+tree[id].r )>>1;
49     if ( x <= mid )
50         update(lid,x,val);
51     else
52         update(rid,x,val);
53     push_up(id);
54 }
55 
56 int query( int id,int l,int r )
57 {
58     if ( tree[id].l==l&&tree[id].r==r )
59         return tree[id].mx;
60     int mid = ( tree[id].l+tree[id].r )>>1;
61     if ( r <= mid )
62         return query(lid,l,r);
63     if ( l > mid )
64         return query(rid,l,r);
65     return max(query(lid,l,mid),query(rid,mid+1,r));
66 }
67 
68 
69 
70 int main(void)
71 {
72     int n,m;
73     while ( scanf("%d%d",&n,&m)!=EOF )
74     {
75         for ( int i = 1; i<= n;i++ )
76         scanf("%d",&a[i]);
77     build(1,1,n);
78     string str;
79     while ( m-- )
80     {
81         cin>>str;
82         if ( str[0]==‘Q‘ )
83         {
84             int t1,t2;scanf("%d%d",&t1,&t2);
85             int ans = query(1,t1,t2);
86             printf("%d\n",ans);
87         }
88         else if ( str[0]==‘U‘ )
89         {
90             int t1,t2;scanf("%d%d",&t1,&t2);
91             update(1,t1,t2);
92         }
93         else
94             break;
95     }
96 
97     }
98     return 0;
99 }