hdu1754 I Hate It

 1 #include <iostream>
 2 #include <string.h>
 3 #define maxn 200005
 4 //#define max(a,b) a>b?a:b
 5 int segment[maxn<<2];
 6 int N,M;
 7 int max(int a,int b){
 8     return a>b?a:b;
 9 }
10 void pushUp(int rt){
11     segment[rt] = max(segment[rt<<1],segment[rt<<1|1]);
12 }
13 void buildTree(int left,int right,int rt){
14     if(left == right){
15         scanf("%d",segment+rt);
16         return ;
17     }
18     int mid = (left + right ) >> 1;
19     buildTree(left,mid,rt<<1);
20     buildTree(mid+1,right,rt<<1|1);
21     pushUp(rt);
22 }
23 
24 void update(int rt,int index,int value,int left,int right){
25  if(left == right ){
26      segment[rt] = value;
27      return ;
28  }
29  int mid = (left + right ) >> 1;
30  if(mid >= index)
31      update(rt<<1,index,value,left,mid);
32  else
33      update(rt<<1|1,index,value,mid+1,right);
34  pushUp(rt);
35 }
36 //拆分区间,直至找到子区间;
37 int query(int left,int right,int rt,int L,int R){
38     if(left >= L && right <= R){
39         return segment[rt];
40     }
41     int mid = (left + right) >> 1;
42     int max_num  = -1;
43     if( L <= mid){
44         max_num = max(max_num,query(left,mid,rt<<1,L,R));
45     }
46     if( R > mid){
47         max_num = max(max_num,query(mid+1,right,rt<<1|1,L,R));
48     }
49     return max_num;
50 }
51 int main()
52 {
53     char op[2];
54     int A,B;
55     while(scanf("%d %d",&N,&M)!=EOF){
56         buildTree(1,N,1);
57         for(int i = 0 ; i < M ; i++){
58             scanf("%s%d%d",op,&A,&B);
59             if(op[0]==‘Q‘)
60                 printf("%d\n",query(1,N,1,A,B));
61             else
62                 update(1,A,B,1,N);
63         }
64     }
65     return 0;
66 }