HDU1754

来源：互联网发布：苍神录java下载编辑：程序博客网时间：2024/06/10 00:33
#include<iostream>#include<cstring>#include<cstdio>#define maxn 200002#define ll __int64//线段树入门作，执行更改某个值，找到区间最大值的操作 using namespace std;ll num[maxn];struct node{ll max,l,r;}tree[maxn*20];ll build(ll root,ll left,ll right)//建的时候就记录max {tree[root].l=left;tree[root].r=right;if(tree[root].l==tree[root].r){tree[root].max=num[left];//cout<<tree[root].max<<endl;    return tree[root].max;}else{ll mid=(left+right)/2;    ll a=build(root*2,left,mid);ll b=build(root*2+1,mid+1,right);tree[root].max=max(a,b); //cout<<max(a,b)<<endl;return max(a,b);}}ll find(ll root,ll left,ll right)//找的时候不能换left，right {//cout<<tree[root].l<<" "<<tree[root].r<<endl;//cout<<left<<" "<<right<<endl;if((tree[root].l>right)||(tree[root].r<left))return 0;if((left<=tree[root].l)&&(tree[root].r<=right)){//cout<<tree[root].max<<endl;return tree[root].max;    }ll a=find(root*2,left,right);ll b=find(root*2+1,left,right);return max(a,b); }ll update(ll root,ll pos,ll val)//更新后还要更新以上区间的值,换pos点为val {if(tree[root].l==tree[root].r&&tree[root].l==pos)//考虑情况要全面 {    tree[root].max=val;    //cout<<tree[root].max<<" "<<tree[root].l<<endl;return tree[root].max;    }    if(tree[root].l>pos||tree[root].r<pos)     return tree[root].max;ll a=update(root*2,pos,val);ll b=update(root*2+1,pos,val);tree[root].max=max(a,b);return tree[root].max;}int main(){ll n,m;while(~scanf("%I64d%I64d",&n,&m)){for(int i=1;i<=n;i++)scanf("%I64d",&num[i]);build(1,1,n);//cout<<tree[1].max<<endl;char c;ll x,y; for(int i=1;i<=m;i++){getchar () ;              scanf ("%c%I64d%I64d", &c, &x, &y) ;              if (c == 'Q')              {                  printf ("%d\n", find (1, x, y)) ;              }              else              {                  num[x] = y ;                  update (1, x, y) ;              }  }}}
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