题面：

线段树，不知道为什么WA了四个点，希望有大佬来帮忙调一下。

代码：

#include <bits/stdc++.h>
using namespace std;
const int N = 200010;
int a[N], tr[N<<2], tg[N<<2];
int ls(int p) { return p << 1; }
int rs(int p) { return p << 1 | 1; }
void up(int p) { tr[p] = max(tr[ls(p)], tr[rs(p)]); }
void build(int p, int pl, int pr)
{
	tg[p] = 0;
	if (pl == pr) { tr[p] = a[pl]; return ; }
	int mid = (pl + pr) >> 1; build(ls(p), pl, mid), build(rs(p), mid + 1, pr), up(p);
}
void addtg(int p, int pl, int pr, int d) { tg[p] += d, tr[p] += d; }
void down(int p, int pl, int pr)
{
	if (tg[p])
	{
		int mid = (pl + pr) >> 1;
		addtg(ls(p), pl, mid, tg[p]), addtg(rs(p), mid + 1, pr, tg[p]), tg[p] = 0;
	}
}
void add(int l, int r, int p, int pl, int pr, int d)
{
	if (l <= pl && pr <= r) { addtg(p, pl, pr, d); return ; }
	down(p, pl, pr); int mid = (pl + pr) >> 1;
	if (l <= mid) add(l, r, ls(p), pl, mid, d);
	if (r > mid) add(l, r, rs(p), mid + 1, pr, d);
	up(p);
}
int ask(int l, int r, int p, int pl, int pr)
{
	if (l <= pl && pr <= r) return tr[p];
	down(p, pl, pr); int ret = 0, mid = (pl + pr) >> 1;
	if (l <= mid) ret = max(ret, ask(l, r, ls(p), pl, mid));
	if (r > mid) ret = max(ret, ask(l, r, rs(p), mid + 1, pr));
	return ret;
}
void upd_1(int rt, int l, int r, int idx, int add)
{
	if (l == r) { tr[rt] += add; return ; }
	int mid = (l + r) / 2;
	if (idx <= mid) upd_1(rt * 2, l, mid, idx, add);
	else upd_1(rt * 2 + 1, mid + 1, r, idx, add);
	up(rt);
}

int main()
{
//	freopen("score.in", "r", stdin);
//	freopen("score.out", "w", stdout);
	int T; scanf("%d", &T);
	while (T--)
	{
		memset(a, 0, sizeof(a)), memset(tr, 0, sizeof(tr)), memset(tg, 0, sizeof(tg));
		int n, m; scanf("%d%d", &n, &m);
		for (int i = 1; i <= n; i++) scanf("%d", &a[i]);
		build(1, 1, n);
		while (m--)
		{
			int l, r; char op; scanf("\n%c %d %d", &op, &l, &r);
			if (op == 'U') upd_1(1, 1, n, l, r - l);
			else printf("%d\n", ask(l, r, 1, 1, n));
		}
	}
	return 0;
}