线段树模板

#include <cstdio>

#include <algorithm>

#include<iostream>

#include<cmath>

 

using namespace std;

 

#define lson l , m , rt << 1

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

#define root 1 , N , 1

#define LL long long

const int maxn = ;

LL add[maxn<<2];

LL sum[maxn<<2];

/*void PushUp(int rt)   //求区间和的时候用这个

{

    sum[rt] = sum[rt<<1] + sum[rt<<1|1];

}*/

void PushUp(int rt)  //求最值的时候用这个

{

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

}

/*void PushDown(int rt,int m)   //注意！！！点更新时不要这个函数

{

    if (add[rt])

    {

        add[rt<<1] += add[rt];

        add[rt<<1|1] += add[rt];

        sum[rt<<1] += add[rt] * (m - (m >> 1));

        sum[rt<<1|1] += add[rt] * (m >> 1);

        add[rt] = 0;

    }

}*/

void build(int l,int r,int rt)  //包含了n个数据的输入, l和rt均传入1，r传入个数

{

    add[rt] = 0;

    if (l == r)

    {

        scanf("%lld",&sum[rt]);

        return ;

    }

    int m = (l + r) >> 1;

    build(lson);

    build(rson);

    PushUp(rt);

}

void update(int p, int sc, int l, int r, int rt)  //点更新

{

if (l == r)

      {

sum[rt] = sc;

return;

}

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

if (p <= m) update(p, sc, lson);

else update(p, sc, rson);

PushUp(rt);

}

/*void update(int L,int R,int c,int l,int r,int rt)  //(段更新)L、R为要加或减的区间， c是加的值， l、r为总区间， rt为根

{

    if (L <= l && r <= R)

    {

        add[rt] += c;

        sum[rt] += (LL)c * (r - l + 1);

        return ;

    }

    //PushDown(rt , r - l + 1);

    int m = (l + r) >> 1;

    if (L <= m) update(L , R , c , lson);

    if (m < R) update(L , R , c , rson);

    PushUp(rt);

}*/

LL query(int L,int R,int l,int r,int rt)

{

    if (L <= l && r <= R)

    {

        return sum[rt];

    }

    //PushDown(rt , r - l + 1);

    int m = (l + r) >> 1;

    LL ret = 0;

   /* if (L <= m) ret += query(L , R , lson); //求区间和的时候这样写

    if (m < R) ret += query(L , R , rson);*/

    if (L <= m) ret = max(ret , query(L , R , lson));   //找最大值的时候这样写同时PushUp也要改

    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);

        while (m --) {

            char op[2];

            int a , b;

            scanf("%s%d%d",op,&a,&b);

            if (op[0] == 'Q') printf("%d\n",query(a , b , 1 , n , 1));

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

        }

    }

    return 0;

}