//2.【非递归版】
void solve(int root) {
static Nod stk[maxn];
memset(vis, 0, sizeof(vis));
stk[0].init(root, E[root]);
int len = 1;
int lev = 0;
cnt = 0;
route[root] = 0; //update route!
while(1) {
Nod & cur = stk[len-1];
//here, b means current Nod, nxt means nxt's pointer(as buf.nxt)!
if(false == vis[cur.b]) {
vis[cur.b] = 1;
F[++ cnt] = cur.b;
rmq[cnt] = lev;
P[cur.b] = cnt;
} else if(cur.nxt == -1) {
if(--len == 0) break;
F[++ cnt] = stk[len-1].b;
rmq[cnt] = -- lev;
} else {
int & i = cur.nxt;
if(!vis[buf[i].b]) {
route[buf[i].b] = route[cur.b] + V[i];
//update route!
lev ++;
stk[len ++].init(buf[i].b, E[buf[i].b]);
}
i = buf[i].nxt;
}
}
st.init(2 * n - 1);
}
void solve(int root) {
memset(vis, 0, sizeof(vis));
route[root] = cnt = 0;
dfs(root, 0);
st.init(2*n-1);
}