hdu 1754 I Hate It

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题目链接 hdu 1754 I Hate It

线段树单点更新求区间最大值

//线段树单点更新#include<iostream>#include<cstdio>#include<cstdlib>#define maxn 222222#define lson l,m,rt<<1#define rson m+1,r,rt<<1|1using namespace std;int MAX[maxn<<2];void pushup(int rt){    MAX[rt]=max(MAX[rt<<1],MAX[rt<<1|1]);}void build(int l,int r,int rt){    if(l==r)    {        scanf("%d",&MAX[rt]);        return ;    }    int m=(l+r)>>1;    build(lson);    build(rson);    pushup(rt);}int query(int L,int R,int l,int r,int rt){    if(L<=l&&r<=R) return MAX[rt];    int m =(l+r)>>1;    int MAX=-1;    if(L<=m) MAX=max(MAX,query(L,R,lson));    if(R>m)  MAX=max(MAX,query(L,R,rson));    return MAX;}void update(int p,int sc,int l,int r,int rt){    if(l==r)    {        MAX[rt]=sc;        return ;    }    int m =(l+r)>>1;    if(p<=m) update(p,sc,lson);    else update(p,sc,rson);    pushup(rt);}int main(){    int n,m;    while(~scanf("%d%d",&n,&m))    {        build(1,n,1);        while(m--)        {            char op;            int a,b;            scanf(" %c%d%d",&op,&a,&b);            if(op=='Q') printf("%d\n",query(a,b,1,n,1));            else update(a,b,1,n,1);        }    }}

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