线段树 区间查询最大值，单体修改 hdu 1754

 #include<cstdio>
 #include<algorithm>
 #include<string.h>
 #include<math.h>
 #include<queue>
 #include<iostream>
 using namespace std;
 const int maxn=2e5+;
 int ary[maxn];
 struct node
 {
     int l,r,val;
 }tree[maxn<<];
 void push_up(int cur)
 {
     tree[cur].val=max(tree[cur*].val,tree[cur*+].val);
 }
 void build(int l,int r,int cur)
 {
     tree[cur].l=l,tree[cur].r=r;
     tree[cur].val=;
     if(l==r){
         tree[cur].val=ary[l];
         return;
     }
     int mid=(l+r)/;
     build(l,mid,cur*);
     build(mid+,r,cur*+);
     push_up(cur);
 }
 int query(int l,int r,int cur)
 {

     if(l<=tree[cur].l&&r>=tree[cur].r)
         return tree[cur].val;
     int mid=(tree[cur].l+tree[cur].r)/;
     int ans=;
     if(l<=mid) ans=max(ans,query(l,r,cur*));
     if(r>mid)  ans=max(ans,query(l,r,cur*+));
     return ans;
 }
 void Update(int base,int price,int cur)
 {
     if(tree[cur].l==tree[cur].r){
         tree[cur].val=price;
         return;
     }
     int mid=(tree[cur].l+tree[cur].r)/;
     if(base<=mid) Update(base,price,cur*);
     else          Update(base,price,cur*+);
     push_up(cur);
 }
 int main()
 {
     int n,m;
     while(scanf("%d%d",&n,&m)!=EOF){
         for(int i=;i<=n;i++) scanf("%d",&ary[i]);
         build(,n,);
         while(m--){
             char tmp;
             cin>>tmp;
             if(tmp=='Q'){
                 int l,r;
                 scanf("%d%d",&l,&r);
                 int ans=query(l,r,);
                 printf("%d\n",ans);
             }
             else{
                 int l,r;
                 scanf("%d%d",&l,&r);
                 Update(l,r,);
             }
         }
     }
     return ;
 }