HDU 1754 I Hate It(线段树求区间最大值)

来源：互联网发布：中泰铁路知乎编辑：程序博客网时间：2024/05/17 23:42
#include<iostream>#include<stdio.h>#include<math.h>#include<stdlib.h>#include<algorithm>#define N 200005using namespace std;int max(int a, int b){    return a>b?a:b;}int val[N];int maxn[N<<2];void build(int l, int r, int rt){    if(l==r)    {        scanf("%d", &val[l]);//        printf("%d:%d ", l, val[l]);        maxn[rt]=val[l];        return ;    }    int mid=(l+r)/2;    build(l, mid, rt<<1);    build(mid+1, r, rt<<1|1);    maxn[rt]=max(maxn[rt<<1], maxn[rt<<1|1]);//    cout << maxn[rt] <<" " <<maxn[rt<<1]<<" "<< maxn[rt<<1|1] <<" ";}void update(int l, int r, int pos, int v, int rt){    if(l==r)    {        maxn[rt]=v;        return;    }    int mid=(l+r)/2;    if(pos<=mid) update(l, mid, pos, v, rt<<1);    else update(mid+1, r, pos, v, rt<<1|1);    maxn[rt]=max(maxn[rt<<1], maxn[rt<<1|1]);//    cout << maxn[rt<<1] << " " << maxn[rt<<1|1] << endl;}int query(int L, int R, int l, int r, int rt){    if(L<=l&&r<=R)    {        return maxn[rt];    }    int mid=(l+r)/2;    int s1=-1, s2=-1;    if(L<=mid) s1= query(L, R, l, mid, rt<<1);    if(R>mid)  s2= query(L, R, mid+1, r, rt<<1|1);    return max(s1, s2);}int main(){    int n, m;    char s[2];    int a, b;    while(scanf("%d%d", &n,&m)!=EOF)    {        build(1, n, 1);        for(int i=0; i<m; i++)        {            scanf("%s", &s);            if(s[0]=='Q')            {                scanf("%d%d", &a, &b);                printf("%d\n",query(a, b, 1, n, 1));            }            else if(s[0]=='U')            {                scanf("%d%d", &a, &b);                update(1, n, a, b, 1);            }        }    }    return 0;}