hdu 1754 I Hate It

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题目：http://acm.hdu.edu.cn/showproblem.php?pid=1754

寻找区间最大值。

#include <iostream>#include <cstdio>#define lson l,m,rt<<1#define rson m+1,r,rt<<1|1using namespace std;const int maxn = 200005;int tree[maxn<<2];char str[10];void PushUp(int rt){    tree[rt] = max(tree[rt<<1],tree[rt<<1|1]);}void build(int l, int r, int rt){    if (l == r){        scanf("%d",&tree[rt]);        return;    }    int  m = (l + r) >> 1;    build (lson);    build (rson);    PushUp(rt);}void update(int id ,int p, int l, int r, int rt){    if (l == r){        tree[rt] = p;        return ;    }    int m = (l + r) >> 1;    if (id <= m)        update(id,p,lson);    else        update(id,p,rson);    PushUp(rt);}int query(int L,int R,int l,int r,int rt){    if(L <= l && r <= R){        return tree[rt];    }    int m = (l + r)>>1;    int ret = 0;    if(L <= m)        ret = max(ret,query(L, R, lson));    if(R > m)        ret = max(ret,query(L, R, rson));    return ret;}int main(){    int n,m;    while(~scanf("%d%d",&n,&m)){        build(1,n,1);        int a,b;        while(m--){            scanf("%s",str);            scanf("%d%d",&a,&b);            if(str[0] == 'Q')                printf("%d\n",query(a,b,1,n,1));            else if(str[0] == 'U')                update(a,b,1,n,1);//            for(int i = 1;i < n*4;i++)//                printf("%d ",tree[i]);//            printf("\n");        }    }    return 0;}

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