HDU Aragorn's Story

题目链接

树抛入门裸题，这题是区间修改单点查询，于是套树状数组就OK了

代码：

#include <cstdio>
#include <cstring>
#include <vector>
#include <algorithm>
using namespace std;

const int N = 50005;

inline int lowbit(int x) {return x&(-x);}

int dep[N], fa[N], son[N], sz[N], top[N], id[N], idx;
vector<int> g[N];

int bit[N];

int n, m, p, val[N];

void dfs1(int u, int f, int d) {
	dep[u] = d;
	sz[u] = 1;
	fa[u] = f;
	son[u] = 0;
	for (int i = 0; i < g[u].size(); i++) {
		int v = g[u][i];
		if (v == f) continue;
		dfs1(v, u, d + 1);
		sz[u] += sz[v];
		if (sz[son[u]] < sz[v])
			son[u] = v;
	}
}

void dfs2(int u, int tp) {
	id[u] = ++idx;
	top[u] = tp;
	if (son[u]) dfs2(son[u], tp);
	for (int i = 0; i < g[u].size(); i++) {
		int v = g[u][i];
		if (v == fa[u] || v == son[u]) continue;
		dfs2(v, v);
	}
}

void add(int x, int v) {
	while (x < N) {
		bit[x] += v;
		x += lowbit(x);
	}
}

void add(int l, int r, int v) {
	add(l, v);
	add(r + 1, -v);
}

void gao(int u, int v, int w) {
	int tp1 = top[u], tp2 = top[v];
	while (tp1 != tp2) {
		if (dep[tp1] < dep[tp2]) {
			swap(tp1, tp2);
			swap(u, v);
		}
		add(id[tp1], id[u], w);
		u = fa[tp1];
		tp1 = top[u];
	}
	if (dep[u] > dep[v]) swap(u, v);
	add(id[u], id[v], w);
}

int query(int x) {
	int ans = 0;
	while (x) {
		ans += bit[x];
		x -= lowbit(x);
	}
	return ans;
}

int main() {
	while (~scanf("%d%d%d", &n, &m, &p)) {
		idx = 0;
		memset(bit, 0, sizeof(bit));
		for (int i = 1; i <= n; i++) {
			scanf("%d", &val[i]);
			g[i].clear();
		}
		int u, v;
		while (m--) {
			scanf("%d%d", &u, &v);
			g[u].push_back(v);
			g[v].push_back(u);
		}
		dfs1(1, -1, 1);
		dfs2(1, 1);
		for (int i = 1; i <= n; i++) add(id[i], id[i], val[i]);
		char q[2];
		int a, b, c;
		while (p--) {
			scanf("%s", q);
			if (q[0] == 'I' || q[0] == 'D') {
				scanf("%d%d%d", &a, &b, &c);
				if (q[0] == 'D') c = -c;
				gao(a, b, c);
			} else {
				scanf("%d", &a);
				printf("%d\n", query(id[a]));
			}
		}
	}
	return 0;
}