【算法系列学习】线段树 单点覆盖，区间查询最大值 [kuangbin带你飞]专题七 线段树 B - I Hate It

https://vjudge.net/contest/66989#overview

 #include<iostream>
 #include<cstdio>
 #include<cstring>
 #include<string>
 #include<algorithm>
 #include<cmath>
 #define lson (i<<1)
 #define rson (i<<1|1)

 using namespace std;
 const int maxn=2e5+;
 int val[maxn];

 struct Seg
 {
     int l,r,lazy,val;
 }tree[maxn<<];

 void push_up(int i)
 {
     tree[i].val=max(tree[lson].val,tree[rson].val);
 }

 void push_down(int i)
 {
     if(tree[i].lazy==-)
     {
         return;
     }
     tree[lson].lazy=tree[lson].val=tree[i].lazy;
     tree[rson].lazy=tree[rson].val=tree[i].lazy;
     tree[i].lazy=-;
 }

 void Build(int l,int r,int i=)
 {
     tree[i].l=l;
     tree[i].r=r;
     tree[i].lazy=-;
     if(l==r)
     {
         tree[i].val=val[l];
         return;
     }
     push_down(i);
     int mid=(tree[i].l+tree[i].r)>>;
     Build(l,mid,lson);
     Build(mid+,r,rson);
     push_up(i);
 }

 int Query(int l,int r,int i=)
 {
     if(tree[i].l==l&&tree[i].r==r)
     {
         return tree[i].val;
     }
     push_down(i);
     int mid=(tree[i].l+tree[i].r)>>;
     if(r<=mid)
     {
         return Query(l,r,lson);
     }
     else if(l>mid)
     {
         return Query(l,r,rson);
     }
     else
     {
         return max(Query(l,mid,lson),Query(mid+,r,rson));
     }
 }

 void Setval(int l,int r,int x,int i=)
 {
     if(tree[i].l==l&&tree[i].r==r)
     {
         tree[i].lazy=tree[i].val=x;
         return;
     }
     push_down(i);
     int mid=(tree[i].l+tree[i].r)>>;
     if(r<=mid)
     {
         Setval(l,r,x,lson);
     }
     else if(l>mid)
     {
         Setval(l,r,x,rson);
     }
     else
     {
         Setval(l,mid,x,lson);
         Setval(mid+,r,x,rson);
     }
     push_up(i);
  }
 int main()
 {
     int n,m;
     while(scanf("%d%d",&n,&m)!=EOF)
     {
         for(int i=;i<=n;i++)
         {
             scanf("%d",&val[i]);
         }
         Build(,n);
         char q[];
         int a,b;
         for(int i=;i<=m;i++)
         {
             scanf("%s%d%d",q,&a,&b);
             if(q[]=='Q')
             {
                 printf("%d\n",Query(a,b));
             }
             else
             {
                 Setval(a,a,b);
             }
         }
     }
     return ;
  }