hdu 1754 I Hate It 线段树 单点更新 区间最值

线段树功能:update:单点更新 query:区间最值

#include <bits/stdc++.h>
#define lson l, m, rt<<1
#define rson m+1, r, rt<<1|1
using namespace std;

const int MAXN = 200008;
int maxs[MAXN<<2];

void build(int l, int r, int rt)
{
    if(l == r)
    {
        scanf("%d", &maxs[rt]);
        return;
    }
    int m = (l + r) >> 1;
    build(lson);
    build(rson);
    maxs[rt] = max(maxs[rt<<1], maxs[rt<<1|1]);
}

int query(int L, int R, int l, int r, int rt)
{
    if(L <= l && r <= R) return maxs[rt];
    int ret = 0;
    int m = (l + r) >> 1;
    if(L <= m) ret = max(ret, query(L, R, lson));
    if(R > m) ret = max(ret, query(L, R, rson));
    return ret;
}

void updata(int p, int news, int l, int r, int rt)
{
    if(l == r)
    {
        maxs[rt] = news;
        return;
    }
    int m = (l + r) >> 1;
    if(p <= m) updata(p, news, lson);
    else updata(p, news, rson);
    maxs[rt] = max(maxs[rt<<1], maxs[rt<<1|1]);
}

int main()
{
//    freopen("in.txt", "r", stdin);
    int n,k;
    while(~scanf("%d%d", &n, &k))
    {
        build(1, n, 1);
        while(k--)
        {
            char s[5];
            scanf("%s", s);
            int a,b;
            scanf("%d%d", &a, &b);
            if(s[0] == 'Q') printf("%d
", query(a, b, 1, n, 1));
            else updata(a, b, 1, n, 1);
        }
    }
    return 0;
}