新用户推荐http://temege.com/p/1/solution/66a310d55ed1c81f72f96654

这里附一个线段树代码也可AC，推荐使用

#include <bits/stdc++.h>
#define int long long
using namespace std;
const int N = 1e5 + 10;
const int INF = 0x3f3f3f3f;
struct node
{
	int l , r , num;
}tree [N];
int a [N] = {} , n , tag[N];
void ctf (int c)
{
	tree [c].num = tree [(c << 1)].num + tree [(c << 1) + 1].num;
}
void buildt (int sp , int l , int r)
{
	tree [sp].l = l;
	tree [sp].r = r;
	if(l == r)
	{
		tree [sp].num = a [l];
		return;
	}
	int mid = l + r >> 1;
	buildt ((sp << 1) , l , mid);
	buildt ((sp << 1) + 1 , mid + 1 , r);
	ctf (sp);
}
void f (int sp)
{
	int mid = tree [sp].l + tree [sp].r >> 1;
	if (tag [sp])
	{
		tree [(sp << 1)].num += tag [sp] * (mid - tree[sp].l + 1);
		tree [(sp << 1) + 1].num += tag [sp] * (tree [sp].r - mid);
		tag [(sp << 1)] += tag [sp];
		tag [(sp << 1) + 1] += tag [sp];
		tag [sp] = 0;
	}
}
void def (int sp , int pt , int nn)
{
	if(tree [sp].l == tree [sp].r)
	{
		tree [sp].num += nn;
		return;
	}
	int mid = tree [sp].l + tree [sp].r >> 1;
	if (pt <= mid) def ((sp << 1) , pt , nn);
	else def((sp << 1) + 1 , pt , nn);
	ctf (sp);
}
void init(int sp , int l , int r , int c)
{
	if(tree [sp].l >= l && tree [sp].r <= r)
	{
		tree [sp].num += (tree [sp].r - tree [sp].l + 1) * c;
		tag [sp] += c;
		return;
	}
	f (sp);
	int mid = tree [sp].l + tree[sp].r >> 1;
	if (l <= mid) init((sp << 1) , l , r , c);
	if (mid < r) init((sp << 1) + 1 , l , r , c);
	ctf (sp);
}
int answ (int sp , int l , int r)
{
	if (tree [sp].l >= l && tree [sp].r <= r)return tree [sp].num;
	f (sp);
	int mid = tree [sp].l + tree [sp].r >> 1;
	int maxn = 0;
	if (l <= mid) maxn = maxn + answ ((sp << 1) , l , r);
	if (mid < r) maxn = maxn + answ ((sp << 1) + 1 , l , r);
	return maxn;
}
signed main()
{
		int T = 1;
	    n = 2;
		for (int i = 1; i <= n; i++) cin >> a [i];
	    buildt (1 , 1 , 2);
	    cout << answ (1 , 1 , 2);
}