2016北京集训测试赛(十一)Problem C: 树链问题
Solution
智障暴力题, 每个点维护一下子树信息, 树剖就好了. 我居然还傻了写了一发毛毛虫...
#include <cstdio>
#include <cctype>
#include <vector>
#include <algorithm>
#include <cstring>
#define vector std::vector
#define max std::max
#define min std::min
#define sort std::sort
#define swap std::swap
namespace Zeonfai
{
inline int getInt()
{
int a = 0, sgn = 1; char c;
while(! isdigit(c = getchar())) if(c == '-') sgn *= -1;
while(isdigit(c)) a = a * 10 + c - '0', c = getchar();
return a * sgn;
}
}
const int N = (int)1e5;
int n, m;
int a[N];
struct query
{
int u, v, val;
inline query(int _u, int _v, int _val) {u = _u; v = _v; val = _val;}
};
struct binaryIndexedTree
{
int a[N + 1];
inline void clear() {memset(a, 0, sizeof(a));}
inline void modify(int pos, int x)
{
for(int i = pos; i <= n; i += i & - i) a[i] += x;
}
inline int query(int pos)
{
int res = 0;
for(int i = pos; i; i -= i & - i) res += a[i];
return res;
}
inline int query(int L, int R)
{
if(L > R) return 0; else return query(R) - query(L - 1);
}
}BIT[2];
struct tree
{
struct node
{
vector<int> edg;
int hvy, tp, pre;
int sz, dep;
int id[2], L, R;
vector<query> qry;
int ans;
inline void clear() {edg.clear(); qry.clear();}
}nd[N + 1];
inline void clear() {for(int i = 1; i <= n; ++ i) nd[i].clear();}
inline void addEdge(int u, int v) {nd[u].edg.push_back(v); nd[v].edg.push_back(u);}
void getSize(int u, int pre)
{
nd[u].sz = 1; nd[u].dep = ~ pre ? nd[pre].dep + 1 : 0; nd[u].hvy = -1; nd[u].pre = pre;
for(auto v : nd[u].edg) if(v != pre)
{
getSize(v, u); nd[u].sz += nd[v].sz;
if(nd[u].hvy == -1 || nd[v].sz > nd[nd[u].hvy].sz) nd[u].hvy = v;
}
}
int clk;
void decomposition(int u, int tp)
{
nd[u].tp = tp; nd[u].id[0] = ++ clk;
if(~ nd[u].hvy) decomposition(nd[u].hvy, tp);
for(auto v : nd[u].edg) if(v != nd[u].pre && v != nd[u].hvy) decomposition(v, v);
}
inline void decomposition() {getSize(1, -1); clk = 0; decomposition(1, 1);}
void getSection(int u)
{
if(nd[u].hvy == -1) return;
nd[u].L = (int)1e9; nd[u].R = -1;
for(auto v : nd[u].edg) if(v != nd[u].pre) getSection(v), nd[u].L = min(nd[u].L, nd[v].id[1]), nd[u].R = max(nd[u].R, nd[v].id[1]);
}
inline void getSection() {getSection(1);}
inline int getLCA(int u, int v)
{
while(nd[u].tp != nd[v].tp)
{
if(nd[nd[u].tp].dep > nd[nd[v].tp].dep) u = nd[nd[u].tp].pre;
else if(nd[nd[u].tp].dep < nd[nd[v].tp].dep) v = nd[nd[v].tp].pre;
else u = nd[nd[u].tp].pre, v = nd[nd[v].tp].pre;
}
if(nd[u].dep > nd[v].dep) swap(u, v);
return u;
}
inline int getPath(int u, int v, int opt)
{
int res = 0;
if(opt)
{
if(nd[u].hvy == -1) u = nd[u].pre; if(nd[v].hvy == -1) v = nd[v].pre;
while(nd[u].tp != nd[v].tp)
{
if(nd[nd[u].tp].dep > nd[nd[v].tp].dep) res += BIT[1].query(nd[nd[u].tp].L, nd[u].R), u = nd[nd[u].tp].pre;
else if(nd[nd[u].tp].dep < nd[nd[v].tp].dep) res += BIT[1].query(nd[nd[v].tp].L, nd[v].R), v = nd[nd[v].tp].pre;
else res += BIT[1].query(nd[nd[u].tp].L, nd[u].R) + BIT[1].query(nd[nd[v].tp].L, nd[v].R), u = nd[nd[u].tp].pre, v = nd[nd[v].tp].pre;
}
if(nd[u].dep > nd[v].dep) swap(u, v);
res += BIT[1].query(nd[u].L, nd[v].R);
}
else
{
while(nd[u].tp != nd[v].tp)
{
if(nd[nd[u].tp].dep > nd[nd[v].tp].dep) res += BIT[0].query(nd[nd[u].tp].id[0], nd[u].id[0]), u = nd[nd[u].tp].pre;
else if(nd[nd[u].tp].dep < nd[nd[v].tp].dep) res += BIT[0].query(nd[nd[v].tp].id[0], nd[v].id[0]), v = nd[nd[v].tp].pre;
else res += BIT[0].query(nd[nd[u].tp].id[0], nd[u].id[0]) + BIT[0].query(nd[nd[v].tp].id[0], nd[v].id[0]), u = nd[nd[u].tp].pre, v = nd[nd[v].tp].pre;
}
if(nd[u].dep > nd[v].dep) swap(u, v);
res += BIT[0].query(nd[u].id[0], nd[v].id[0]);
}
return res;
}
int getAnswer(int u)
{
nd[u].ans = 0;
for(auto v : nd[u].edg) if(v != nd[u].pre) nd[u].ans += getAnswer(v);
for(auto qry : nd[u].qry)
{
int cur = qry.val;
cur += getPath(qry.u, qry.v, 1) - getPath(qry.u, qry.v, 0);
nd[u].ans = max(nd[u].ans, cur);
}
for(int i = 0; i < 2; ++ i) BIT[i].modify(nd[u].id[i], nd[u].ans);
return nd[u].ans;
}
inline int getAnswer() {return getAnswer(1);}
}T;
inline int cmp(int a, int b)
{
int preA = T.nd[a].pre, preB = T.nd[b].pre;
if(preA == -1) return 1; else if(preB == -1) return 0; else return T.nd[preA].id[0] < T.nd[preB].id[0];
}
int main()
{
#ifndef ONLINE_JUDGE
freopen("tchain.in", "r", stdin);
freopen("tchain.out", "w", stdout);
#endif
using namespace Zeonfai;
for(int cs = getInt(); cs --;)
{
n = getInt(), m = getInt();
T.clear(); for(int i = 0; i < 2; ++ i) BIT[i].clear();
for(int i = 1; i < n; ++ i)
{
int u = getInt(), v = getInt();
T.addEdge(u, v);
}
T.decomposition();
for(int i = 1; i <= n; ++ i) a[i] = i; sort(a + 1, a + n + 1, cmp); for(int i = 1; i <= n; ++ i) T.nd[a[i]].id[1] = i;
T.getSection();
for(int i = 0; i < m; ++ i)
{
int u = getInt(), v = getInt(), val = getInt();
T.nd[T.getLCA(u, v)].qry.push_back(query(u, v, val));
}
printf("%d\n", T.getAnswer());
}
}