线段树（区间最大值查询和点修改）——I Hate It ( HDU 1754 )

#define lc (d<<1)
#define rc (d<<1|1)
#define mid ( l+r >>1)

const int Max = 200005;
int a[Max];
struct Tr
{
int mx;
}tr[Max*3];
void Push(int root)
{
tr[root].mx = max(tr[lc].mx , tr[rc].mx);
}
void build (int root, int l, int r)
{
if( l == r )//到达最下面的子节点
{
tr[root].mx = a[l];直接从数组中赋值
return ;
}
build(lc, l, mid);
build(rc, mid+1, r);
Push(root);
}

int query(int root,  int l ,  int r,  int L,  int R )//L，R表示查询区间
{
if( L==l && r == R)
{
return tr[root].mx;
}

if( R <= mid)
return query(lc, l, mid, L, R);
else if (L > mid)
return query( rc, mid+1, r, L, R);
else
return max(query(lc, l, mid, L, mid) ,query(rc, mid+1, r, mid+1, R) );
}

void update (int root,  int l,  int r,  int loc,  int value)
{
if(l == r)
{
tr[d].mx = value;
return;
}
if( loc <= mid) update(lc, l, mid, loc, k);
else  update( rc, mid+1, r, loc, k);
Push(root);
}

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>

using namespace std;

#define lc (d<<1)
#define rc (d<<1|1)
#define mid ( l+r >>1)
const int Max = 200005;

int a[Max];

struct Tr
{
int mx;
}tr[Max*3];

void Push(int d)
{
tr[d].mx = max(tr[lc].mx , tr[rc].mx);
}

void build (int d, int l, int r)
{
if( l == r )
{
tr[d].mx = a[l];
return ;
}
build(lc, l, mid);
build(rc, mid+1, r);
Push(d);
}

int query(int d,  int l ,  int r,  int L,  int R )
{
if( L==l && r == R)
{
//cout << ":"<<d <<endl;
return tr[d].mx;
}

if( R <= mid)
return query(lc, l, mid, L, R);
else if (L > mid)
return query( rc, mid+1, r, L, R);
else
return max(query(lc, l, mid, L, mid) ,query(rc, mid+1, r, mid+1, R) );
}

void update (int d,  int l,  int r,  int loc,  int k)
{
if(l == r)
{
tr[d].mx = k;
return ;
}
if( loc <= mid) update(lc, l, mid, loc, k);
else  update( rc, mid+1, r, loc, k);
Push(d);
}

int main()
{
int n,m;
while(~scanf("%d%d",&n,&m))
{
memset(tr, 0, sizeof(tr));
for(int i=1;i<=n;i++)
{
scanf("%d", &a[i]);
}
build(1, 1, n);
char c[2];
while(m--)
{
int a,b;
scanf("%s%d%d",c,&a,&b);
if(c[0]=='U')
update(1,1,n,a,b);
if(c[0]=='Q')
printf("%d\n",query(1,1,n,a,b));
}
}
}