树状数组 1 ：单点修改，区间查询

题目：

#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<algorithm>
#include<queue>
#include<stack>
#include<string>
#include<map>
#include<sstream>
#include<vector>
#include<ctime>
#include<list>
#define int long long
using namespace std;
int a[1000005];
int c[1000005];
int n,q;
int lowbit(int x)
{
    return x&(-x);
}
int change(int x,int k)
{
    while(x<=n)
    {
        c[x]+=k;
        x+=lowbit(x);
    }
}
int sum(int x)
{
    int ans=0;
    while(x>0)
    {
        ans+=c[x];
        x-=lowbit(x);
    }
    return ans;
}
signed main()
{
    cin>>n>>q;
    for(int i=1;i<=n;i++)
    {
        scanf("%lld",&a[i]);
        change(i,a[i]);
    }
    while(q--)
    {
        int k,x,y;
        scanf("%lld %lld %lld",&k,&x,&y);
        if(k==1)
        {
            change(x,y);
        }
        else
        {
            printf("%lld\n",sum(y)-sum(x-1));
        }
    }
    return 0;
}