OJ-Problems-Source/HDOJ/3894_autoAC.cpp
2016-09-04 14:17:41 +08:00

143 lines
3.3 KiB
C++

#include <iostream>
#include <stdio.h>
using namespace std;
const int N = 1000005;
struct e{
int v;
e* nxt;
}es[N<<1], *fir[N], stk[N];
int n, m, en, p;
int E, W;
bool hasFood[N];
int eastNum[N], westNum[N], par[N];
int minp[N], t[N], que[N], dep[N];
inline void add_e(int u, int v){
es[en].v = v;
es[en].nxt = fir[u];
fir[u] = &es[en++];
}
template <typename T>
void getNum(T& a){
a = 0;
char ch;
while(true){
ch = getchar();
if(ch >= '0' && ch <= '9') break;
}
a = ch - '0';
while(true){
ch = getchar();
if(ch < '0' || ch > '9') break;
a = a * 10 + ch - '0';
}
}
bool input(){
if(scanf("%d%d%d%d", &n, &m, &E, &W)== EOF) return false;
int i, u, v;
en = 0;
for(i = 1; i <= n; i++){
fir[i] = NULL;
hasFood[i] = false;
}
for(i = 1; i < n; i++){
getNum<int>(u);
getNum<int>(v);
add_e(u, v);
add_e(v, u);
}
scanf("%d", &p);
for(i = 1; i <= p; i++){
getNum(u);
hasFood[i] = true;
}
return true;
}
inline bool isEast(int u){ return u <= E; }
inline bool has(int u) { return hasFood[u]; }
inline bool isWest(int u){ return u >= n - W + 1; }
inline void push(int v, int p, int& top){
eastNum[v] = westNum[v] = 0;
if(isEast(v)){
eastNum[v]++;
}else if(isWest(v)){
westNum[v]++;
}
++top;
stk[top].v = v;
stk[top].nxt = fir[v];
par[v] = p;
}
typedef bool (*fun)(int u);
void bfs(int st, int* ar, fun check){
int l, r, u, v, num;
e* cur;
l = r = num = 0;
que[r++] = st; dep[st] = 0;
if(check(st)){
ar[num++] = 0;
}
while(l != r && num < p){
u = que[l++];
for(cur = fir[u]; cur; cur = cur->nxt){
if((v = cur->v) != par[u]){
que[r++] = v; par[v] = u; dep[v] = dep[u] + 1;
if(check(v)){
ar[num++] = dep[v];
if(num >= p) break;
}
}
}
}
}
void solve(){
int top = -1, u, v, est, wst, ans;
int i, maxt;
push(1, -1, top);
while(top >= 0){
u = stk[top].v;
if(stk[top].nxt == NULL){
if(eastNum[u] == 0 && westNum[u] == W){
wst = u;
est = par[u];
break;
}
if(eastNum[u] == E && westNum[u] == 0){
wst = par[u];
est = u;
break;
}
if(par[u] >= 1){
eastNum[par[u]] += eastNum[u];
westNum[par[u]] += westNum[u];
}
top--;
continue;
}else{
v = stk[top].nxt->v;
stk[top].nxt = stk[top].nxt->nxt;
if(v != par[u]){
push(v, u, top);
}
}
}
par[est] = wst;
par[wst] = est;
bfs(wst, minp, isWest);
bfs(est, t, has);
ans = 0;
maxt = -1;
for(i = 0; i < p; i++){
if(t[i] < maxt + 1) t[i] = maxt + 1;
maxt = t[i];
if(ans < t[i] + minp[p - i - 1]){
ans = t[i] + minp[p - i - 1];
}
}
ans++;
cout<<ans<<endl;
}
int main() {
while(input()) solve();
return 0;
}