P2486 [SDOI2011]染色

R63914703

Luogu/P2486/P2486.cpp

@@ -0,0 +1,174 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+const int N = 100005;
+
+int n, m, u, v, c, color[N];
+char op;
+vector<int> g[N];
+
+// Heavy Path Decomposition
+int cnt, dep[N], id[N], siz[N], fa[N], son[N], top[N], w[N];
+void dfs1(int, int);
+void dfs2(int u, int t);
+void modify_path(int, int, int);
+int query_path(int, int);
+
+// Segment Tree
+void pushup(int);
+void pushdown(int);
+void build(int, int, int);
+void modify(int, int, int, int);
+int query_sum(int, int, int);
+int query_color(int, int);
+
+int main() {
+    cin >> n >> m;
+    for (int i = 1; i <= n; i++) {
+        cin >> color[i];
+    }
+    for (int i = 1; i < n; i++) {
+        cin >> u >> v;
+        g[u].push_back(v);
+        g[v].push_back(u);
+    }
+    dfs1(1, 0);
+    dfs2(1, 1);
+    build(1, 1, n);
+    while (m--) {
+        cin >> op >> u >> v;
+        if (op == 'C') {
+            cin >> c;
+            modify_path(u, v, c);
+        } else {
+            cout << query_path(u, v) << endl;
+        }
+    }
+    return 0;
+}
+
+// === Heavy Path Decomposition ===
+
+void dfs1(int u, int f) {
+    dep[u] = dep[f] + 1;
+    fa[u] = f;
+    siz[u] = 1;
+    for (int v : g[u]) {
+        if (v == f) continue;
+        dfs1(v, u);
+        siz[u] += siz[v];
+        if (siz[son[u]] < siz[v]) son[u] = v;
+    }
+}
+
+void dfs2(int u, int t) {
+    id[u] = ++cnt;
+    w[cnt] = color[u];
+    top[u] = t;
+    if (!son[u]) return;
+    dfs2(son[u], t);
+    for (int v : g[u]) {
+        if (v == fa[u]) continue;
+        if (v == son[u]) continue;
+        dfs2(v, v);
+    }
+}
+
+void modify_path(int u, int v, int c) {
+    while (top[u] != top[v]) {
+        if (dep[top[u]] < dep[top[v]]) swap(u, v);
+        modify(1, id[top[u]], id[u], c);
+        u = fa[top[u]];
+    }
+    if (dep[u] < dep[v]) swap(u, v);
+    modify(1, id[v], id[u], c);
+}
+
+int query_path(int u, int v) {
+    int res = 0;
+    while (top[u] != top[v]) {
+        if (dep[top[u]] < dep[top[v]]) swap(u, v);
+        res += query_sum(1, id[top[u]], id[u]);
+        res -= (query_color(1, id[top[u]]) == query_color(1, id[fa[top[u]]]));
+        u = fa[top[u]];
+    }
+    if (dep[u] < dep[v]) swap(u, v);
+    res += query_sum(1, id[v], id[u]);
+    return res;
+}
+
+// === Segment Tree ===
+
+struct node {
+    int l, r, s, d, lc, rc;
+
+    node()
+        : l(0), r(0), s(0), d(0), lc(0), rc(0) {}
+    node(int _l, int _r)
+        : l(_l), r(_r), s(0), d(0), lc(0), rc(0) {}
+} tr[N << 2];
+
+inline void pushup(int u) {
+    tr[u].s = tr[u << 1].s + tr[u << 1 | 1].s - (tr[u << 1].rc == tr[u << 1 | 1].lc);
+    tr[u].lc = tr[u << 1].lc;
+    tr[u].rc = tr[u << 1 | 1].rc;
+}
+
+inline void pushdown(int u) {
+    auto &root = tr[u], &left = tr[u << 1], &right = tr[u << 1 | 1];
+    if (!tr[u].d) return;
+    left.d = right.d = root.d;
+    left.lc = left.rc = right.lc = right.rc = root.d;
+    left.s = right.s = 1;
+    root.d = 0;
+}
+
+void build(int u, int l, int r) {
+    tr[u] = node(l, r);
+    if (l == r) {
+        tr[u].lc = tr[u].rc = w[l];
+        tr[u].s = 1;
+        return;
+    }
+    int mid = l + r >> 1;
+    build(u << 1, l, mid);
+    build(u << 1 | 1, mid + 1, r);
+    pushup(u);
+}
+
+void modify(int u, int l, int r, int c) {
+    if (l <= tr[u].l && tr[u].r <= r) {
+        tr[u].d = tr[u].lc = tr[u].rc = c;
+        tr[u].s = 1;
+        return;
+    }
+    pushdown(u);
+    int mid = tr[u].l + tr[u].r >> 1;
+    if (l <= mid) modify(u << 1, l, r, c);
+    if (r > mid) modify(u << 1 | 1, l, r, c);
+    pushup(u);
+}
+
+int query_sum(int u, int l, int r) {
+    if (l <= tr[u].l && tr[u].r <= r) {
+        return tr[u].s;
+    }
+    int mid = tr[u].l + tr[u].r >> 1;
+    int res = 0;
+    pushdown(u);
+    if (l <= mid) res += query_sum(u << 1, l, r);
+    if (r > mid) res += query_sum(u << 1 | 1, l, r);
+    if (l <= mid && r > mid) res -= (tr[u << 1].rc == tr[u << 1 | 1].lc);
+    return res;
+}
+
+int query_color(int u, int x) {
+    if (tr[u].l == x && tr[u].r == x) {
+        return tr[u].lc;
+    }
+    int mid = tr[u].l + tr[u].r >> 1;
+    pushdown(u);
+    if (x <= mid) return query_color(u << 1, x);
+    return query_color(u << 1 | 1, x);
+}