B - I Hate It

 1 #include<cstdio>
 2 #include<string.h>
 3 using namespace std;
 4 int ans;
 5 int max1=0;
 6 int a[200010];
 7 struct Node{
 8     int left;
 9     int right;
10     int max;
11 }node[800010];
12 void TreeMake(int l,int r,int i)
13 {
14     node[i].left=l;
15     node[i].right=r;
16     node[i].max=0;
17     if(l==r)
18     {
19         node[i].max=a[l];//是a[l]!!!!!
20         return;
21     }
22     else
23     {
24         int mid=(l+r)/2;
25         TreeMake(l,mid,2*i);
26         TreeMake(mid+1,r,2*i+1);
27         node[i].max=node[2*i].max>node[2*i+1].max?node[2*i].max:node[2*i+1].max;//注意更新最大值，回溯
28     }
29 }
30 void Updata_tree(int l,int i)
31 {
32     if(node[i].left==l&&node[i].right==l)
33     {
34          node[i].max=ans;
35          return;
36     }
37 
38     else{
39         int mid=(node[i].left+node[i].right)/2;
40         if(l<=mid) Updata_tree(l,2*i);
41         if(l>mid) Updata_tree(l,2*i+1);
42         node[i].max=node[2*i].max>node[2*i+1].max?node[2*i].max:node[2*i+1].max;//注意回溯！！
43     }
44 
45 }
46 
47 void Query_tree(int l,int r,int i)
48 {
49    //if(node[i].left==l&&node[i].right==r)
50      //   return node[i].max;
51    //
52    if(node[i].left>=l&&node[i].right<=r)
53    {
54        if(max1<node[i].max)
55             max1=node[i].max;
56        return;
57    }
58    int mid=(node[i].left+node[i].right)/2;
59    if(r<=mid) Query_tree(l,r,2*i);
60    else if(l>mid) Query_tree(l,r,2*i+1);
61    else
62    {
63        Query_tree(l,r,2*i);
64        Query_tree(l,r,2*i+1);
65    }
66 }
67 
68 
69 
70 int main()
71 {
72     int n,m;
73     char ch[10];
74     while(scanf("%d %d",&n,&m)!=EOF)
75     {
76         for(int i=1;i<=n;i++)
77             scanf("%d",&a[i]);
78             TreeMake(1,n,1);
79         while(m--)
80         {
81             scanf("%s",ch);
82             int x,y;
83             scanf("%d %d",&x,&y);
84             max1=0;
85             if(ch[0]==‘Q‘)
86             {
87                 Query_tree(x,y,1);//查询(x,y)区间
88                 printf("%d\n",max1);
89             }
90             if(ch[0]==‘U‘)
91             {
92                 ans=y;
93                 Updata_tree(x,1);
94             }
95         }
96     }
97     return 0;
98 }