1 文本格式
#include <bits/stdc++.h>
using namespace std;
typedef long long LL;
const int maxn = 500010;
const int INF = 0x3f3f3f3f;
int Begin[maxn], Next[maxn], To[maxn], e, n, m;
int size[maxn], son[maxn], top[maxn], fa[maxn], dis[maxn], p[maxn], id[maxn], End[maxn];
int cnt, tot, a[maxn], f[maxn][2];
struct matrix {
int g[2][2];
matrix() { memset(g, 0, sizeof(g)); }
matrix operator*(const matrix& b) const
{
matrix c;
for (int i = 0; i <= 1; i++)
for (int j = 0; j <= 1; j++)
for (int k = 0; k <= 1; k++)
c.g[i][j] = max(c.g[i][j], g[i][k] + b.g[k][j]);
return c;
}
} Tree[maxn], g[maxn];
inline void PushUp(int root) {
Tree[root] = Tree[root << 1] * Tree[root << 1 | 1];
}
inline void Build(int root, int l, int r) {
if (l == r) {
Tree[root] = g[id[l]];
return;
}
int Mid = l + r >> 1;
Build(root << 1, l, Mid);
Build(root << 1 | 1, Mid + 1, r);
PushUp(root);
}
inline matrix Query(int root, int l, int r, int L, int R) {
if (L <= l && r <= R) return Tree[root];
int Mid = l + r >> 1;
if (R <= Mid) return Query(root << 1, l, Mid, L, R);
if (Mid < L) return Query(root << 1 | 1, Mid + 1, r, L, R);
return Query(root << 1, l, Mid, L, R) *
Query(root << 1 | 1, Mid + 1, r, L, R);
}
inline void Modify(int root, int l, int r, int pos) {
if (l == r) {
Tree[root] = g[id[l]];
return;
}
int Mid = l + r >> 1;
if (pos <= Mid)
Modify(root << 1, l, Mid, pos);
else
Modify(root << 1 | 1, Mid + 1, r, pos);
PushUp(root);
}
inline void Update(int x, int val) {
g[x].g[1][0] += val - a[x];
a[x] = val;
while (x) {
matrix last = Query(1, 1, n, p[top[x]], End[top[x]]);
Modify(1, 1, n, p[x]);
matrix now = Query(1, 1, n, p[top[x]], End[top[x]]);
x = fa[top[x]];
g[x].g[0][0] +=
max(now.g[0][0], now.g[1][0]) - max(last.g[0][0], last.g[1][0]);
g[x].g[0][1] = g[x].g[0][0];
g[x].g[1][0] += now.g[0][0] - last.g[0][0];
}
}
inline void add(int u, int v) {
To[++e] = v;
Next[e] = Begin[u];
Begin[u] = e;
}
inline void DFS1(int u) {
size[u] = 1;
int Max = 0;
f[u][1] = a[u];
for (int i = Begin[u]; i; i = Next[i]) {
int v = To[i];
if (v == fa[u]) continue;
dis[v] = dis[u] + 1;
fa[v] = u;
DFS1(v);
size[u] += size[v];
if (size[v] > Max) {
Max = size[v];
son[u] = v;
}
f[u][1] += f[v][0];
f[u][0] += max(f[v][0], f[v][1]);
}
}
inline void DFS2(int u, int t) {
top[u] = t;
p[u] = ++cnt;
id[cnt] = u;
End[t] = cnt;
g[u].g[1][0] = a[u];
g[u].g[1][1] = -INF;
if (!son[u]) return;
DFS2(son[u], t);
for (int i = Begin[u]; i; i = Next[i]) {
int v = To[i];
if (v == fa[u] || v == son[u]) continue;
DFS2(v, v);
g[u].g[0][0] += max(f[v][0], f[v][1]);
g[u].g[1][0] += f[v][0];
}
g[u].g[0][1] = g[u].g[0][0];
}
int main() {
scanf("%d%d", &n, &m);
for (int i = 1; i <= n; i++) scanf("%d", &a[i]);
for (int i = 1; i <= n - 1; i++) {
int u, v;
scanf("%d%d", &u, &v);
add(u, v);
add(v, u);
}
dis[1] = 1;
DFS1(1);
DFS2(1, 1);
Build(1, 1, n);
for (int i = 1; i <= m; i++) {
int x, val;
scanf("%d%d", &x, &val);
Update(x, val);
matrix ans = Query(1, 1, n, 1, End[1]);
printf("%d\n", max(ans.g[0][0], ans.g[1][0]));
}
return 0;
}
2 代码格式
#include <bits/stdc++.h>using namespace std;typedef long long LL;const int maxn = 500010;
const int INF = 0x3f3f3f3f;int Begin[maxn], Next[maxn], To[maxn], e, n, m;
int size[maxn], son[maxn], top[maxn], fa[maxn], dis[maxn], p[maxn], id[maxn], End[maxn];
int cnt, tot, a[maxn], f[maxn][2];struct matrix {int g[2][2];matrix() { memset(g, 0, sizeof(g)); }matrix operator*(const matrix& b) const {matrix c;for (int i = 0; i <= 1; i++)for (int j = 0; j <= 1; j++)for (int k = 0; k <= 1; k++)c.g[i][j] = max(c.g[i][j], g[i][k] + b.g[k][j]);return c;}
} Tree[maxn], g[maxn]; inline void PushUp(int root) {Tree[root] = Tree[root << 1] * Tree[root << 1 | 1];
}inline void Build(int root, int l, int r) {if (l == r) {Tree[root] = g[id[l]];return;}int Mid = l + r >> 1;Build(root << 1, l, Mid);Build(root << 1 | 1, Mid + 1, r);PushUp(root);
}inline matrix Query(int root, int l, int r, int L, int R) {if (L <= l && r <= R) return Tree[root];int Mid = l + r >> 1;if (R <= Mid) return Query(root << 1, l, Mid, L, R);if (Mid < L) return Query(root << 1 | 1, Mid + 1, r, L, R);return Query(root << 1, l, Mid, L, R) *Query(root << 1 | 1, Mid + 1, r, L, R);
}inline void Modify(int root, int l, int r, int pos) {if (l == r) {Tree[root] = g[id[l]];return;}int Mid = l + r >> 1;if (pos <= Mid)Modify(root << 1, l, Mid, pos);elseModify(root << 1 | 1, Mid + 1, r, pos);PushUp(root);
}inline void Update(int x, int val) {g[x].g[1][0] += val - a[x];a[x] = val;while (x) {matrix last = Query(1, 1, n, p[top[x]], End[top[x]]);Modify(1, 1, n, p[x]);matrix now = Query(1, 1, n, p[top[x]], End[top[x]]);x = fa[top[x]];g[x].g[0][0] +=max(now.g[0][0], now.g[1][0]) - max(last.g[0][0], last.g[1][0]);g[x].g[0][1] = g[x].g[0][0];g[x].g[1][0] += now.g[0][0] - last.g[0][0];}
}inline void add(int u, int v) {To[++e] = v;Next[e] = Begin[u];Begin[u] = e;
}inline void DFS1(int u) {size[u] = 1;int Max = 0;f[u][1] = a[u];for (int i = Begin[u]; i; i = Next[i]) {int v = To[i];if (v == fa[u]) continue;dis[v] = dis[u] + 1;fa[v] = u;DFS1(v);size[u] += size[v];if (size[v] > Max) {Max = size[v];son[u] = v;}f[u][1] += f[v][0];f[u][0] += max(f[v][0], f[v][1]);}
}inline void DFS2(int u, int t) {top[u] = t;p[u] = ++cnt;id[cnt] = u;End[t] = cnt;g[u].g[1][0] = a[u];g[u].g[1][1] = -INF;if (!son[u]) return;DFS2(son[u], t);for (int i = Begin[u]; i; i = Next[i]) {int v = To[i];if (v == fa[u] || v == son[u]) continue;DFS2(v, v);g[u].g[0][0] += max(f[v][0], f[v][1]);g[u].g[1][0] += f[v][0];}g[u].g[0][1] = g[u].g[0][0];
}int main() {scanf("%d%d", &n, &m);for (int i = 1; i <= n; i++) scanf("%d", &a[i]);for (int i = 1; i <= n - 1; i++) {int u, v;scanf("%d%d", &u, &v);add(u, v);add(v, u);}dis[1] = 1;DFS1(1);DFS2(1, 1);Build(1, 1, n);for (int i = 1; i <= m; i++) {int x, val;scanf("%d%d", &x, &val);Update(x, val);matrix ans = Query(1, 1, n, 1, End[1]);printf("%d\n", max(ans.g[0][0], ans.g[1][0]));}return 0;
}
