树状数组真的很精美，码量小，还很快，比线段树快多了[滑稽]。
一维树状数组
单点修改，区间查询
例题：
不多说，代码：
#include <bits/stdc++.h>
using namespace std;
const int N = 5e5+5;
int n, m, c[N];
int lowbit(int k) {return k&-k;}
void add(int x, int d) {for (; x <= n; x += lowbit(x)) c[x] += d;}
int ask(int x) {
int sum = 0;
for (; x; x -= lowbit(x)) sum += c[x];
return sum;
}
int main() {
ios::sync_with_stdio(0);
cin >> n >> m;
for (int i = 1, x; i <= n; ++i) {
cin >> x;
add(i, x);
}
for (int op, x, y; m--; ) {
cin >> op >> x >> y;
if (op == 1) add(x, y);
else cout << ask(y)-ask(x-1) << endl;
}
return 0;
}
区间修改，单点查询
例题：
loj #131. 树状数组 2
luogu P3368【模板】树状数组 2
不多说，代码：
#include <bits/stdc++.h>
using namespace std;
const int N = 5e5+5;
int n, m, a[N], c[N];
int lowbit(int k) {return k&-k;}
void add(int x, int d) {for (; x <= n; x += lowbit(x)) c[x] += d;}
int ask(int x) {
int sum = 0;
for (; x; x -= lowbit(x)) sum += c[x];
return sum;
}
int main() {
ios::sync_with_stdio(0);
cin >> n >> m;
for (int i = 1; i <= n; ++i) cin >> a[i];
for (int op, x, y, k; m--; ) {
cin >> op >> x;
if (op == 1) {
cin >> y >> k;
add(x, k);
add(y+1, -k);
}
else cout << a[x]+ask(x) << '\n';
}
return 0;
}