Spoj375 Query on a tree 裸·树链剖分

#include<bits/stdc++.h>
using namespace std;
const int INF = 0x3f3f3f3f;
const int maxn = 100000 + 10;

void read(int &n) {
int f = 1; n = 0;
char ch = getchar();
while(ch < '0' || ch > '9') { if(ch == '-') f = -1; ch = getchar(); }
while(ch >='0' && ch <='9') { n = n * 10 + ch - 48; ch = getchar(); }
n *= f;
}

struct SegmentTree {
int Max[maxn * 4];
void init() { memset(Max, 0, sizeof(Max)); }
void Push_up(int u) {
int lc = u << 1, rc = u << 1 | 1;
Max[u] = max(Max[lc], Max[rc]);
}
void update(int u, int l, int r, int sl, int sr, int v) {
if(sl <= l && r <= sr) { Max[u] = v; return; }

int mid = (l + r) >> 1, lc = u << 1, rc = u << 1 | 1;
if(sl <= mid) update(lc, l, mid, sl, sr, v);
if(sr > mid) update(rc, mid+1, r, sl, sr, v);
Push_up(u);
}
int query(int u, int l, int r, int sl, int sr) {
if(sl <= l && r <= sr) return Max[u];

int Tmp = -INF;
int mid = (l + r) >> 1, lc = u << 1, rc = u << 1 | 1;
if(sl <= mid) Tmp = max(Tmp, query(lc, l, mid, sl, sr));
if(sr > mid) Tmp = max(Tmp, query(rc, mid+1, r, sl, sr));

return Tmp;
}
}ST;

struct Edge {
int from, to, dist;
}e[maxn];
int Begin[maxn], Next[maxn*2], To[maxn*2], E;
void Add(int x, int y) {
To[++E] = y;
Next[E] = Begin[x];
Begin[x] = E;
}

int cnt, n;
int tid[maxn], son[maxn], top[maxn], fa[maxn], size[maxn], dep[maxn];

void dfs(int cur, int f, int d) {
dep[cur] = d;
size[cur] = 1;
for(int i=Begin[cur]; i; i=Next[i]) {
int t = To[i];
if(t != f) {
dfs(t, cur, d+1);
fa[t] = cur;
size[cur] += size[t];
if(son[cur] == -1 || size[t] > size[son[cur]])
son[cur] = t;
}
}
}
void dfs(int cur, int tp) {
top[cur] = tp;
tid[cur] = ++cnt;
if(son[cur] == -1) return;
dfs(son[cur], tp);
for(int i=Begin[cur]; i; i=Next[i]) {
int t = To[i];
if(t != fa[cur] && t != son[cur])
dfs(t, t);
}
}
void init() {
E = cnt = 0;
ST.init();
memset(fa, 0, sizeof(fa));
memset(son, -1, sizeof(son));
memset(Begin, 0, sizeof(Begin));

for(int i=1; i<n; i++) {
scanf("%d%d%d", &e[i].from, &e[i].to, &e[i].dist);
Add(e[i].from, e[i].to); Add(e[i].to, e[i].from);
}
dfs(1, 1, 1); dfs(1, 1);

for(int i=1; i<n; i++) {
if(dep[e[i].to] < dep[e[i].from]) swap(e[i].to, e[i].from);
ST.update(1, 2, cnt, tid[e[i].to], tid[e[i].to], e[i].dist);
}
}
int Getmax(int x, int y) {
int ans = -INF;
while(top[x] != top[y]) {
if(dep[top[x]] < dep[top[y]]) swap(x, y);
ans = max(ans, ST.query(1, 2, cnt, tid[top[x]], tid[x]));
x = fa[top[x]];
}
if(dep[x] > dep[y]) swap(x, y);
if(x != y) ans = max(ans, ST.query(1, 2, cnt, tid[x]+1, tid[y]));
return ans;
}
char s[20];
int T, u, v;
int main() {
#ifndef ONLINE_JUDGE
freopen("
4000
data.txt", "r", stdin);
freopen("ans.txt", "w", stdout);
#endif
read(T);
while(T--) {
read(n); init();
while(scanf("%s", s) == 1 && s[0] != 'D') {
read(u), read(v);
if(s[0] == 'C')
ST.update(1, 2, cnt, tid[e[u].to], tid[e[u].to], v);
else
printf("%d\n", Getmax(u, v));
}
}
return 0;
}