1 #include <cstdio>
 2 #include <cstring>
 3 #include <algorithm>
 4 using namespace std;
 5 
 6 const int LEN = 200020;
 7 
 8 struct line
 9 {
10     int left;
11     int right;
12     int ma;
13 }line[LEN*5];
14 
15 void buildt(int l, int r, int step)  //建树，同时初始化区间最值
16 {
17     line[step].left = l;
18     line[step].right = r;
19     line[step].ma = 0;
20     if (l == r)
21         return;
22     int mid = (l + r) / 2;
23     buildt(l, mid, step*2);
24     buildt(mid+1, r, step*2+1);
25 }
26 
27 int update(int l, int r, int value, int step)  //更新函数，返回整型
28 {
29     if (line[step].left == line[step].right){  //如果到达最深处的节点，则说明找到了需要更新的单点，赋值
30         line[step].ma = value;
31         return max(line[step/2*2].ma, line[step/2*2+1].ma); //返回该节点与其兄弟节点的较大值
32     }
33     int mid = (line[step].left + line[step].right) / 2;  //向下继续搜索
34     if (r <= mid)
35         line[step].ma = update(l, r, value, step*2);
36     else if (l > mid)
37         line[step].ma = update(l, r, value, step*2+1);
38     else{             //如果目标线段处于目前线段的中点的两边，则同时搜索该节点的两个子节点，并取较大值
39         line[step].ma = max(update(l, mid, value, step*2), update(mid+1, r, value, step*2+1));
40     }
41     return max(line[step/2*2].ma, line[step/2*2+1].ma);  //返回该节点与其兄弟节点的较大值
42 }
43 
44 int dfs(int l, int r, int step)  //dfs找答案
45 {
46     if (l == line[step].left && r == line[step].right) //如果找到目标区间，返回值
47         return line[step].ma;
48     int mid = (line[step].left + line[step].right) / 2;
49     if (r <= mid)
50         return dfs(l, r, step*2);
51     else if (l > mid)
52         return dfs(l, r, step*2+1);
53     else{
54         return max(dfs(l, mid, step*2), dfs(mid+1, r, step*2+1)); //返回该节点与其兄弟节点的较大值
55     }
56 }
57 
58 
59 int main()
60 {
61     int n, m;
62     //freopen("in.txt", "r", stdin);
63     while(scanf("%d %d", &n, &m) != EOF){
64         buildt(1, n, 1);
65         for(int i = 1; i <= n; i++){
66             int t;
67             scanf("%d", &t);
68             update(i, i, t, 1);
69         }
70         for(int i = 0; i < m; i++){
71             char query[2];
72             int a, b;
73             scanf("%s %d %d", query, &a, &b);
74             if (query[0] == ‘U‘)
75                 update(a, a, b, 1);
76             else if (query[0] == ‘Q‘){
77                 printf("%d\n", dfs(a, b, 1));
78             }
79         }
80     }
81     return 0;
82 }