POJ3468 A Simple Problem with Integers(区间更新＋区间查询＋差分)

题目链接：http://poj.org/problem?id=3468

参考：https://blog.csdn.net/qq_39562952/article/details/81298043

#include <iostream>
#include <cstring>
#include <cstdio>
#define mem(a,b) memset(a,b,sizeof(a));
using namespace std;
typedef long long ll;
const int maxn = 500005;
const ll INF = 0x3f3f3f3f;
ll n,q,m;
ll a[maxn],b[maxn],c[maxn];
ll lowbit(ll t) {//取出t的最低位１
    return t&(-t);
}
ll getsum(ll x) {
    ll ans = 0;
    for(int i = x; i > 0; i -= lowbit(i)) {
        ans += x*b[i]-c[i];
    }
    return ans;
}
void update(ll x,ll v) {
    for(int i = x; i <= n; i+=lowbit(i)) {
        b[i] += v;
        c[i] += v*(x-1);
    }
}
int main()
{

    cin >> n >> q;
    for(int i = 1; i <= n; i++) {
        cin >> m;
        a[i] = a[i-1] + m;
    }
    char p;
    ll x, y, z;
    for(int i = 1; i <= q; i++) {
        cin >> p;
        if(p == 'Q') {
            cin >> x >> y;
            cout <<(a[y] - a[x-1] + getsum(y) - getsum(x-1))<< endl;
        }
        else {
            cin >> x >> y >> z;
            update(x,z);
            update(y+1,-z);
//            for(int i = 1; i <= n; i++) {
//                cout << b[i] << " " << c[i] << endl;
//            }
        }
    }
    return 0;
}