HDU1754 I Hate It

解题思路：求区间最大值，线段树模板题，不解释：

#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
#define inf 0x3f3f3f3f
#define lson l, m, rt << 1
#define rson m+1, r, rt << 1 | 1
const int maxn = 200005;
int A[maxn<<2], n, m, a, b;
char str[10];

void Max(int rt)
{
    A[rt] = max(A[rt<<1], A[rt<<1 | 1]);
}

void Build(int l, int r, int rt)
{
    if(l == r)
    {
        scanf("%d", &A[rt]);
        return ;
    }
    int m = (l + r) >> 1;
    Build(lson);
    Build(rson);
    Max(rt);
}

void Update(int p, int score, int l, int r, int rt)
{
    if(l == r)
    {
        A[rt] = score;
        return ;
    }
    int m = (l + r) >> 1;
    if(p <= m) Update(p, score, lson);
    else Update(p, score, rson);
    Max(rt);
}

int Query(int ll, int rr, int l, int r, int rt)
{
    if(ll <= l && rr >= r) return A[rt];
    int m = (l + r) >> 1;
    int max1 = -inf;
    if(ll <= m) max1 = max(max1, Query(ll, rr, lson));
    if(rr > m) max1 = max(max1, Query(ll, rr, rson));
    return max1;
}

int main()
{
    while(~scanf("%d %d", &n, &m))
    {
        Build(1, n, 1);
        while(m--)
        {
            scanf("%s%d%d", str, &a, &b);
            if(str[0] == 'Q')
            {
                int ans = Query(a, b, 1, n, 1);
                printf("%d
", ans);
            }
            else Update(a, b, 1, n, 1);
        }
    }
    return  0;
}