Hdu1754单点更新

　　和上一题差不多，单点更新，求和，求最值，求乘积之类的，都可以照着搞。

#include <cstdio>

#include <cstring>

#include <algorithm>

#include <climits>

#include <string>

#include <iostream>

#include <map>

#include <cstdlib>

#include <list>

#include <set>

#include <queue>

#include <stack>



using namespace std;

#define lson l,mid,rt<<1

#define rson mid+1,r,rt<<1|1

int sum[888888];

void up(int rt)

{

    sum[rt] = max(sum[rt << 1], sum[rt << 1 | 1]);

}

void build(int l, int r, int rt)

{

    if (l == r){

        scanf("%d", &sum[rt]); return;

    }

    int mid = (l + r) >> 1;

    build(lson);

    build(rson);

    up(rt);

}



int ask(int L, int R, int l, int r, int rt)

{

    if (L <= l&&r <= R)return sum[rt];

    int mid = (l + r) >> 1;

    int ans = 0;

    if (L <= mid) ans = max(ans, ask(L, R, lson));

    if (R>mid) ans = max(ans, ask(L, R, rson));

    return ans;

}



void update(int key, int add, int l, int r, int rt)

{

    if (l == r){

        sum[rt] = add; return;

    }

    int mid = (l + r) >> 1;

    if (key <= mid) update(key, add, lson);

    else update(key, add, rson);

    up(rt);

}

int main()

{

    int n, m;

    int a, b;

    char str[100];

    while (scanf("%d%d", &n, &m) != EOF){

        build(1, n, 1);

        for (int i = 0; i<m; i++){

            scanf("%s", str);

            scanf("%d%d", &a, &b);

            if (str[0] == 'U'){

                update(a, b, 1, n, 1);

            }

            else printf("%d\n", ask(a, b, 1, n, 1));

        }

    }

    return 0;

}