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| #include <cstdio>
#include <algorithm>
using namespace std;
typedef long long LL;
const unsigned INF = 2147483648u;
int n, m;
const int maxn = 100005;
int fa[maxn], top[maxn], siz[maxn], dep[maxn], tid[maxn], son[maxn], id[maxn], dfn[maxn], root;
unsigned lazy[maxn * 4], mi[maxn * 4], A[maxn];
int h[maxn], cnte = 1, clock = 0;
struct edge_type {
int to, next;
} edge[maxn * 2];
void ins(int x, int y) {
edge[++cnte].to = y;
edge[cnte].next = h[x];
h[x] = cnte;
edge[++cnte].to = x;
edge[cnte].next = h[y];
h[y] = cnte;
}
void add(int x, unsigned val) {
mi[x] = val;
lazy[x] = val;
}
void pd(int x) {
if (lazy[x]) {
add(x << 1, lazy[x]);
add(x << 1 | 1, lazy[x]);
lazy[x] = 0;
}
}
void pu(int x) {
mi[x] = min(mi[x << 1], mi[x << 1 | 1]);
}
void change(int now, int l, int r, int ll, int rr, unsigned val) {
if (ll <= l && r <= rr) return add(now, val);
int mid = (l + r) >> 1;
pd(now);
if (ll <= mid) change(now << 1, l, mid, ll, rr, val);
if (rr > mid) change(now << 1 | 1, mid + 1, r, ll, rr, val);
pu(now);
}
int dfs1(int now, int father, int deep) {
fa[now] = father; dep[now] = deep; siz[now] = 1;
for (int i = h[now]; i; i = edge[i].next) {
if (edge[i].to == father) continue;
siz[now] += dfs1(edge[i].to, now, deep + 1);
if (siz[edge[i].to] > siz[son[now]])
son[now] = edge[i].to;
}
return siz[now];
}
void dfs2(int now, int father, int tp) {
tid[now] = ++clock; top[now] = tp; id[clock] = now;
if (son[now]) {
dfs2(son[now], now, tp);
for (int i = h[now]; i; i = edge[i].next) {
if (edge[i].to == father || edge[i].to == son[now]) continue;
dfs2(edge[i].to, now, edge[i].to);
}
}
dfn[now] = clock;
}
void build(int now, int l, int r) {
if (l == r) {
mi[now] = A[id[l]];
return;
}
int mid = (l + r) >> 1;
build(now << 1, l, mid);
build(now << 1 | 1, mid + 1, r);
pu(now);
}
int lca(int x, int y) {
while (top[x] != top[y]) {
if (dep[top[x]] < dep[top[y]]) swap(x, y);
x = fa[top[x]];
}
if (dep[x] < dep[y]) swap(x, y);
return y;
}
void CHANGE(int x, int y, unsigned v) {
while (top[x] != top[y]) {
if (dep[top[x]] < dep[top[y]]) swap(x, y);
change(1, 1, n, tid[top[x]], tid[x], v);
x = fa[top[x]];
}
if (dep[x] < dep[y]) swap(x, y);
change(1, 1, n, tid[y], tid[x], v);
}
int wson(int x, int y) {
int lst;
while (top[x] != top[y]) {
lst = top[x];
x = fa[top[x]];
}
if (x == y) return lst;
return son[y];
}
unsigned query(int now, int l, int r, int ll, int rr) {
if (ll <= l && r <= rr) return mi[now];
pd(now);
int mid = (l + r) >> 1;
unsigned ret = INF;
if (ll <= mid) ret = min(ret, query(now << 1, l, mid, ll, rr));
if (rr > mid) ret = min(ret, query(now << 1 | 1, mid + 1, r, ll, rr));
return ret;
}
unsigned QUERY(int x) {
if (root == x) return query(1, 1, n, 1, n);
if (tid[root] < tid[x] || tid[root] > dfn[x])
return query(1, 1, n, tid[x], dfn[x]);
int ws = wson(root, x);
unsigned ret = INF;
ret = min(ret, query(1, 1, n, 1, tid[ws] - 1));
ret = min(ret, query(1, 1, n, dfn[ws] + 1, n));
return ret;
}
int main() {
int opt, x, y;
unsigned z;
scanf("%d%d", &n, &m);
for (int i = 1; i < n; ++i) {
scanf("%d%d", &x, &y);
ins(x, y);
}
for (int i = 1; i <= n; ++i) scanf("%u", A + i);
scanf("%d", &root);
dfs1(root, 0, 1);
dfs2(root, 0, root);
build(1, 1, n);
for (int i = 1; i <= m; ++i) {
scanf("%d", &opt);
if (opt == 1) scanf("%d", &root);
if (opt == 2) {
scanf("%d%d%u", &x, &y, &z);
CHANGE(x, y, z);
}
if (opt == 3) {
scanf("%d", &x);
printf("%u\n", QUERY(x));
}
}
return 0;
}
|
第三种情况
(注意2^31>MAX_INT，用unsigned)