线段树单点修改与区间查询。

#include<iostream>
#include<cstdio>
using namespace std;

const int N = 500010;
int n, m, a[N], t[N * 4], lazy[N * 4];

void pushup(int r) {
	t[r] = t[r << 1] + t[r << 1 | 1];
}

void build(int p, int l, int r) {
	if(l == r) {
		t[p] = a[l];
		return;
	}
	int mid = (l + r) >> 1;
	build(p << 1, l, mid);
	build(p << 1 | 1, mid + 1, r);
	pushup(p);
}

void update1(int p, int l, int r, int x, int k) {
	if(l == r) {
		t[p] = k;
		return;
	}
	int mid = (l + r) >> 1;
	if(x <= mid)update1(p << 1, l, mid, x, k);
	else update1(p << 1 | 1, mid + 1, r, x, k);
	pushup(p);
}

int query(int p, int l, int r, int x, int y) {
	int ans = 0;
	if(x >= l && r <= y) return t[p];
	int mid = (l + r) >> 1;
	if(x <= mid)ans += query(p << 1, l, mid, x, y);
	if(y > mid)ans += query(p << 1 | 1, mid + 1, r, x, y);
	return ans;
}

int main() {
	cin.tie(0) -> ios::sync_with_stdio(0);
	cin >> n >> m;
	for (int i = 1; i <= n; i++) cin >> a[i];
	build(1, 1, n);
	while(m--) {
		int f; cin >> f;
		if(f == 1) {
			int x, k; cin >> x >> k;
			update1(1, 1, n, x, k);
		}
		if(f == 2) {
			int x, y; cin >> x >> y;
			printf("%d\n", query(1, 1, n, x, y));
		}
	}
	return 0;
}