hdu1754(线段数维护区间最大值)

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题意：给定1-n(n<=200000)个数，然后动态改变一些值，并动态询问区间最大值。

解法：裸的线段树，赛前默写模版回忆下线段树代码。仍然要注意：线段树节点数组一定要开到节点数的三倍长度。

代码：

/******************************************************* author:xiefubao*******************************************************/#pragma comment(linker, "/STACK:102400000,102400000")#include <iostream>#include <cstring>#include <cstdlib>#include <cstdio>#include <queue>#include <vector>#include <algorithm>#include <cmath>#include <map>#include <set>#include <stack>#include <string.h>//freopen ("in.txt" , "r" , stdin);using namespace std;#define eps 1e-8const double pi=acos(-1.0);typedef long long LL;const int Max=300000*3;const int INF=1000000007;struct node{    node* pleft,*pright;    int l,r;    int ma;} nodes[Max];int num[Max];int tot=0;void buildtree(node* p,int left,int right){    p->l=left;    p->r=right;    if(left==right) return;    int mid=(left+right)/2;    tot++;    p->pleft=nodes+tot;    buildtree(p->pleft,left,mid);    tot++;    p->pright=nodes+tot;    buildtree(p->pright,mid+1,right);}int n,m;int update(node* p,int add,int value){    if(p->l==p->r)    {        p->ma=value;        return value;    }    int mid=(p->l+p->r)/2;    if(add<=mid)        update(p->pleft,add,value);    else        update(p->pright,add,value);    return p->ma=max(p->pleft->ma,p->pright->ma);}int query(node* p,int left,int right){    if(p->l==left&&p->r==right)        return p->ma;    int mid=(p->l+p->r)/2;    if(right<=mid)        return query(p->pleft,left,right);    if(left>=mid+1)        return query(p->pright,left,right);    return max(query(p->pleft,left,mid),query(p->pright,mid+1,right));}int main(){    while(scanf("%d%d",&n,&m)==2)    {        tot=0;        buildtree(nodes,1,n+1);        for(int i=1; i<=n; i++)        {            scanf("%d",num+i);            update(nodes,i,num[i]);        }        for(int i=0;i<m;i++)        {            char c;cin>>c;            if(c=='Q')            {                int l,r;scanf("%d%d",&l,&r);                printf("%d\n",query(nodes,l,r));            }            else            {                int l,r;scanf("%d%d",&l,&r);                update(nodes,l,r);            }        }    }    return 0;}

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