poj 3468 线段树（成段增减 区间求和）

题意：

区间增加一个数。（-）

求区间的和。

代码：

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <algorithm>
#include <cstring>
#include <cmath>
#include <stack>
#include <vector>
#include <queue>
#include <map>
#include <climits>
#include <cassert>
#define LL long long
#define lson lo, mi, rt << 1
#define rson mi + 1, hi, rt << 1 | 1

using namespace std;
const int maxn = 100000 + 10;
const int inf = 0x3f3f3f3f;
const double eps = 1e-8;
const double pi = acos(-1.0);
const double ee = exp(1.0);

LL add[maxn << 2];
LL sum[maxn << 2];

void pushup(int rt)
{
    sum[rt] = sum[rt << 1] + sum[rt << 1 | 1];
}

void pushdown(int rt, int mi)
{
    if (add[rt])
    {
        add[rt << 1] += add[rt];
        add[rt << 1 | 1] += add[rt];
        sum[rt << 1] += add[rt] * (mi - (mi >> 1));
        sum[rt << 1 | 1] += add[rt] * (mi >> 1);
        add[rt] = 0;
    }
}

void build(int lo, int hi, int rt)
{
    add[rt] = 0;
    if (lo == hi)
    {
        scanf("%lld", &sum[rt]);
        return;
    }
    int mi = (lo + hi) >> 1;
    build(lson);
    build(rson);
    pushup(rt);
}

void update(int L, int R, int c, int lo, int hi, int rt)
{
    if (L <= lo && hi <= R)
    {
        add[rt] += (LL)c;
        sum[rt] += (LL)c * (hi - lo + 1);
        return;
    }
    pushdown(rt, hi - lo + 1);
    int mi = (lo + hi) >> 1;
    if (L <= mi)
        update(L, R, c, lson);
    if (mi < R)
        update(L, R, c, rson);
    pushup(rt);
}

LL query(int L, int R, int lo, int hi, int rt)
{
    if (L <= lo && hi <= R)
    {
        return sum[rt];
    }
    pushdown(rt, hi - lo + 1);
    int mi = (lo + hi) >> 1;
    LL res = 0;
    if (L <= mi)
        res += query(L, R, lson);
    if (mi < R)
        res += query(L, R, rson);
    return res;
}

int main()
{
    #ifdef LOCAL
    freopen("in.txt", "r", stdin);
    #endif // LOCAL
    int n, q;
    while (~scanf("%d%d", &n, &q))
    {
        build(1, n, 1);
        while (q--)
        {
            char op[2];
            int fr, to, num;
            scanf("%s", op);
            if (op[0] == 'Q')
            {
                scanf("%d%d", &fr, &to);
                printf("%lld\n", query(fr, to, 1, n, 1));
            }
            else
            {
                scanf("%d%d%d", &fr, &to, &num);
                update(fr, to, num, 1, n, 1);
            }
        }
    }
    return 0;
}