线段树点修改模板(HDU1754)

 1 #include<stdio.h>
 2 #define MAXSIZE 200000
 3 int val[MAXSIZE+1];
 4 int max(int x,int y){
 5     return x>y?x:y;
 6 }
 7 struct node{
 8     int Max,left,right;
 9 } tree[MAXSIZE*3];
10 
11 int creat(int root,int left,int right){
12     tree[root].left=left;
13     tree[root].right=right;
14     if(left == right)
15         return tree[root].Max=val[left];
16     int a,b,mid=(left+right)>>1;
17     a=creat(root<<1,left,mid);
18     b=creat(root<<1|1,mid+1,right);
19     return tree[root].Max=max(a,b);
20 }
21 int calculate(int root,int left,int right){
22     if(tree[root].left>right||tree[root].right<left)
23         return 0;
24     if(left<=tree[root].left&&tree[root].right<=right)
25         return tree[root].Max;
26     int a,b;
27     a=calculate(root<<1,left,right);
28     b=calculate(root<<1|1,left,right);
29     return max(a,b);
30 }
31 int update(int root,int pos,int val){
32     if(pos<tree[root].left||tree[root].right<pos)
33         return tree[root].Max;
34     if(tree[root].left==pos&&tree[root].right==pos)
35         return tree[root].Max=val;
36     int a,b;
37     a=update(root<<1,pos,val);
38     b=update(root<<1|1,pos,val);
39     return tree[root].Max=max(a,b);
40 }
41 int main()
42 {
43     int n,m;
44     while(scanf("%d%d",&n,&m)!=EOF){
45         for(int i=1;i<=n;i++){
46             scanf("%d",&val[i]);
47         }
48         creat(1,1,n);
49         for(int i=0;i<m;i++){
50             char op;
51             int a,b;
52             scanf("\n%c%d%d",&op,&a,&b);
53             if(op==‘Q‘)
54                 printf("%d\n",calculate(1,a,b));
55             else
56                 update(1,a,b);
57         }
58     }
59 }