poj 3468__A Simple Problem with Integers（区间求和，成段更新）

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cmath>
using namespace std;
#define lson l , m , rt << 1
#define rson m+1 , r , rt << 1 | 1
#define ll long long
const int maxn=100000+10;
ll sum[maxn << 2], add[maxn << 2];
void Pushup(int rt)
{
    sum[rt] = sum[rt << 1] + sum[rt << 1 | 1];
}
void Pushdown(int rt, int m)    //m表示rt节点代表的区间长度
{
    if(add[rt]) {
        add[rt << 1] += add[rt];
        add[rt << 1 | 1] += add[rt];
        sum[rt << 1] += add[rt] * (m - (m >> 1));   //(m - (m >> 1))表示rt的左孩子增加(m - (m >> 1))个add[rt];
        sum[rt << 1 | 1] += add[rt] * (m >> 1);
        add[rt] = 0;    //处理完之后重置
    }
}
void build(int l, int r, int rt)
{
    add[rt] = 0;
    if(l == r) {
        scanf("%lld", &sum[rt]);
        return ;
    }
    int m = (r + l) >> 1;
    build(lson);
    build(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 = (r + l) >> 1;
    ll ret = 0;
    if(L <= m) {
        ret += query(L, R, lson);
    }
    if(R > m) {
        ret += query(L, R, rson);
    }
    return ret;
}
void update(int L, int R, int c, int l, int r, int rt)
{
    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);
}
int main()
{
    int n, q, a, b, c;
    char s[2];
    scanf("%d%d", &n, &q);  //n个数，q次询问
    build(1, n, 1);
    while(q--) {
        scanf("%s", s);
        if(s[0] == 'Q') {
            scanf("%d%d", &a, &b);
            printf("%lld\n", query(a, b, 1, n, 1));
        } else if(s[0] == 'C') {
            scanf("%d%d%d", &a, &b, &c);
            update(a, b, c, 1, n, 1);
        }
    }
    return 0;
}