poj 2763 Housewife Wind(树链拆分)

#include <cstdio>
#include <cstring>
#include <algorithm>

using namespace std;

const int maxn = 100005;
int N, Q, S, ne;

int first[maxn], jump[maxn * 2];
int id, far[maxn], son[maxn], cnt[maxn], dep[maxn], top[maxn], idx[maxn];

struct Edge {
int u, v, w;
void set (int u, int v, int w) {
this->u = u;
this->v = v;
this->w = w;
}
}ed[maxn * 2];

void dfs_fir (int u, int pre, int d) {
far[u] = pre;
dep[u] = d;
cnt[u] = 1;
son[u] = 0;

for (int i = first[u]; i + 1; i = jump[i]) {
int v = ed[i].v;
if (v == pre)
continue;
dfs_fir(v, u, d+1);
cnt[u] += cnt[v];
if (cnt[son[u]] < cnt[v])
son[u] = v;
}
}

void dfs_sec(int u, int rot) {
top[u] = rot;
idx[u] = id++;

if (son[u])
dfs_sec(son[u], rot);

for (int i = first[u]; i + 1; i = jump[i]) {
int v = ed[i].v;
if (v == far[u] || v == son[u])
continue;
dfs_sec(v, v);
}
}

inline void add_Edge(int u, int v, int w) {
ed[ne].set(u, v, w);
jump[ne] = first[u];
first[u] = ne++;
}

#define lson(x) ((x)<<1)
#define rson(x) (((x)<<1)|1)
typedef long long ll;
int lc[maxn << 2], rc[maxn << 2];
ll s[maxn << 2];

inline void pushup(int u) {
s[u] = s[lson(u)] + s[rson(u)];
}

void build (int u, int l, int r) {
lc[u] = l;
rc[u] = r;
s[u] = 0;

if (l == r)
return;
int mid = (l + r) / 2;
build(lson(u), l, mid);
build(rson(u), mid + 1, r);
pushup(u);
}

void modify (int u, int x, int w) {
if (lc[u] == x && rc[u] == x) {
s[u] = w;
return;
}

int mid = (lc[u] + rc[u]) / 2;
if (x <= mid)
modify(lson(u), x, w);
else
modify(rson(u), x, w);
pushup(u);
}

ll query(int u, int l, int r) {
if (l <= lc[u] && rc[u] <= r)
return s[u];

ll ret = 0;
int mid = (lc[u] + rc[u]) / 2;
if (l <= mid)
ret += query(lson(u), l, r);
if (r > mid)
ret += query(rson(u), l, r);
return ret;
}

void init () {
ne = 0;
id = 1;

int u, v, w;
memset(first, -1, sizeof(first));
for (int i = 0; i < N - 1; i++) {
scanf("%d%d%d", &u, &v, &w);
add_Edge(u, v, w);
add_Edge(v, u, w);
}
dfs_fir(1, 0, 0);
dfs_sec(1, 1);

build(1, 1, N);
for (int i = 0; i < N - 1; i++) {
if (dep[ed[i*2].u] < dep[ed[i*2].v])
swap(ed[i*2].u, ed[i*2].v);
modify(1, idx[ed[i*2].u], ed[i*2].w);
}
}

ll solve (int u, int v) {
ll ret = 0;
int p = top[u], q = top[v];
while (p != q) {
if (dep[p] < dep[q]) {
swap(p, q);
swap(u, v);
}
ret += query(1, idx[p], idx[u]);
u = far[p];
p = top[u];
}

if (u == v)
return ret;

if (dep[u] > dep[v])
swap(u, v);
ret += query(1, idx[son[u]], idx[v]);
return ret;
}

int main () {
while (scanf("%d%d%d", &N, &Q, &S) == 3) {
init();
int k, u, w;
while (Q--) {
scanf("%d%d", &k, &u);
if (k) {
scanf("%d", &w);
modify(1, idx[ed[u*2 - 2].u], w);
} else {
printf("%lld\n", solve(S, u));
S = u;
}
}
}
return 0;
}