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本题链接（AcWing） 点这里
题目描述
给定一个长度为 $N$ 的数列 $A$，以及 $M$ 条指令，每条指令可能是以下两种之一：
C l r d，表示把 $A[l],A[l+1],…,A[r]$ 都加上 $d$。Q l r，表示询问数列中第 $l \sim r$ 个数的和。
对于每个询问，输出一个整数表示答案。
输入格式
第一行两个整数 $N,M$。
第二行 $N$ 个整数 $A[i]$。
接下来 $M$ 行表示 $M$ 条指令，每条指令的格式如题目描述所示。
输出格式
对于每个询问，输出一个整数表示答案。
每个答案占一行。
数据范围
$1 \le N,M \le 10^5$,
$|d| \le 10000$,
$|A[i]| \le 10^9$
输入样例：
10 5
1 2 3 4 5 6 7 8 9 10
Q 4 4
Q 1 10
Q 2 4
C 3 6 3
Q 2 4
输出样例：
4
55
9
15
思路
考虑用树状数组 tr[] 维护差分数组
则求原数组的前缀和
$$ \left\{\begin{matrix} a_1& =& d_1& & & & & & & \\ a_2& =& d_1& +& d_2& & & & & \\ a_3& =& d_1& +& d_2& +& d_3& & & \\ .& .& .& .& .& .& & & & \\ a_n& =& d_1& +& d_2& +& …& +& d_n& \\ \end{matrix}\right. $$
$$s_i=\sum_{i=1}^{n}a_i=\left\{\begin{matrix} d_1& & & & & & & \\ d_1& +& d_2& & & & & \\ d_1& +& d_2& +& d_3& & & \\ .& .& .& .& .& .& & & & \\ d_1& +& d_2& +& …& +& d_n& \\ \end{matrix}\right.$$
我们考虑把后面的矩阵补全：
则
$$s_i=(n+1) \times \sum_{i=1}^{n}d_i-\sum_{i=1}^{n}(i \times d_i)$$
所以我们需要两个树状数组，tr1[] 维护差分数组，tr2[] 维护 $i \times d_i$
代码：
#include <iostream>
using namespace std;
typedef long long LL;
const LL N = 1000010;
LL n, m;
LL a[N];
LL t1[N], t2[N];
inline LL lowbit(LL x)
{
return x & -x;
}
inline void add(LL t[], LL x, LL c)
{
for (LL i = x; i <= n; i += lowbit(i))
t[i] += c;
}
inline LL sum(LL t[], LL x)
{
LL res = 0;
for (LL i = x; i; i -= lowbit(i))
res += t[i];
return res;
}
inline LL psum(LL x)
{
return sum(t1, x) * (x + 1) - sum(t2, x);
}
int main()
{
scanf("%lld%lld", &n, &m);
for (LL i = 1; i <= n; i ++ ) scanf("%lld", &a[i]);
for (LL i = 1; i <= n; i ++ )
{
LL b = a[i] - a[i - 1];
add(t1, i, b);
add(t2, i, b * i);
}
while (m -- )
{
char op[2];
LL l, r, d;
scanf("%s%lld%lld", op, &l, &r);
if (op[0] == '2')
{
printf("%lld\n", psum(r) - psum(l - 1));
}
else
{
scanf("%lld", &d);
add(t1, l, d), add(t2, l, l * d);
add(t1, r + 1, -d), add(t2, r + 1, -d * (r + 1));
}
}
return 0;
}
（后附极限卡常代码，70ms，较优解）
#define qwq optimize
#pragma GCC qwq(1)
#pragma GCC qwq(2)
#pragma GCC qwq(3)
#pragma GCC qwq("Ofast")
#pragma GCC qwq("inline")
#pragma GCC qwq("-fgcse")
#pragma GCC qwq("-fgcse-lm")
#pragma GCC qwq("-fipa-sra")
#pragma GCC qwq("-ftree-pre")
#pragma GCC qwq("-ftree-vrp")
#pragma GCC qwq("-fpeephole2")
#pragma GCC qwq("-ffast-math")
#pragma GCC qwq("-fsched-spec")
#pragma GCC qwq("unroll-loops")
#pragma GCC qwq("-falign-jumps")
#pragma GCC qwq("-falign-loops")
#pragma GCC qwq("-falign-labels")
#pragma GCC qwq("-fdevirtualize")
#pragma GCC qwq("-fcaller-saves")
#pragma GCC qwq("-fcrossjumping")
#pragma GCC qwq("-fthread-jumps")
#pragma GCC qwq("-funroll-loops")
#pragma GCC qwq("-fwhole-program")
#pragma GCC qwq("-freorder-blocks")
#pragma GCC qwq("-fschedule-insns")
#pragma GCC qwq("inline-functions")
#pragma GCC qwq("-ftree-tail-merge")
#pragma GCC qwq("-fschedule-insns2")
#pragma GCC qwq("-fstrict-aliasing")
#pragma GCC qwq("-fstrict-overflow")
#pragma GCC qwq("-falign-functions")
#pragma GCC qwq("-fcse-skip-blocks")
#pragma GCC qwq("-fcse-follow-jumps")
#pragma GCC qwq("-fsched-interblock")
#pragma GCC qwq("-fpartial-inlining")
#pragma GCC qwq("no-stack-protector")
#pragma GCC qwq("-freorder-functions")
#pragma GCC qwq("-findirect-inlining")
#pragma GCC qwq("-fhoist-adjacent-loads")
#pragma GCC qwq("-frerun-cse-after-loop")
#pragma GCC qwq("inline-small-functions")
#pragma GCC qwq("-finline-small-functions")
#pragma GCC qwq("-ftree-switch-conversion")
#pragma GCC qwq("-fqwq-sibling-calls")
#pragma GCC qwq("-fexpensive-optimizations")
#pragma GCC qwq("-funsafe-loop-optimizations")
#pragma GCC qwq("inline-functions-called-once")
#pragma GCC qwq("-fdelete-null-pointer-checks")
#include <iostream>
#include <cstdio>
#define lb(x) (x & (-x))
using namespace std;
typedef long long LL;
const LL N = 100010;
LL n, m;
LL a[N];
LL t1[N], t2[N];
char *p1, *p2, buf[N];
#define nc() (p1 == p2 && (p2 = (p1 = buf) +\
fread(buf, 1, N, stdin), p1 == p2) ? EOF : *p1 ++ )
LL read()
{
LL x = 0, f = 1;
char ch = nc();
while (ch < 48 || ch > 57)
{
if (ch == '-') f = -1;
ch = nc();
}
while (ch >= 48 && ch <= 57)
x = (x << 3) + (x << 1) + (ch ^ 48), ch = nc();
return x * f;
}
char obuf[N], *p3 = obuf;
#define putchar(x) (p3 - obuf < N) ? (*p3 ++ = x) :\
(fwrite(obuf, p3 - obuf, 1, stdout), p3 = obuf, *p3 ++ = x)
inline void write(LL x)
{
if (!x)
{
putchar('0');
return;
}
LL len = 0, k1 = x, c[40];
if (k1 < 0) k1 = -k1, putchar('-');
while (k1) c[len ++ ] = k1 % 10 ^ 48, k1 /= 10;
while (len -- ) putchar(c[len]);
}
inline void add(LL t[], LL x, LL c)
{
for (LL i = x; i <= n; i += lb(i))
t[i] += c;
}
inline LL sum(LL t[], LL x)
{
LL res = 0;
for (LL i = x; i; i -= lb(i))
res += t[i];
return res;
}
inline LL psum(LL x)
{
return sum(t1, x) * (x + 1) - sum(t2, x);
}
int main()
{
n = read(), m = read();
for (LL i = 1; i <= n; i ++ ) a[i] = read();
for (LL i = 1; i <= n; i ++ )
{
LL b = a[i] - a[i - 1];
add(t1, i, b);
add(t2, i, b * i);
}
LL op, l, r, d;
while (m -- )
{
op = read(), l = read(), r = read();
if (op == 2) write(psum(r) - psum(l - 1)), putchar(10);
else
{
d = read();
add(t1, l, d), add(t2, l, l * d);
add(t1, r + 1, -d), add(t2, r + 1, -d * (r + 1));
}
}
fwrite(obuf, p3 - obuf, 1, stdout);
return 0;
}
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