2019杭電多校第三場Blow up the city (支配樹)

建立支配樹， deep[u]+deep[v]-deep[lca(u,v)]即爲答案

#include<iostream>
#include<cstring>
#include<cstdio>
#include<queue>
#include<cstdlib>
#include<cmath>
#include<stack>
#include<map>
#include<string>
#include<vector>
#include<set>
#include<bitset>
#include<algorithm>
using namespace std;
#define ll long long
#define INF 0x3f3f3f3f
#define LINF 0x3f3f3f3f3f3f3f3f
#define ull unsigned long long
#define endl '\n'
#define clr(a, b) memset(a, b, sizeof(a))
#define lowbit(x) x & -x
#define lson rt << 1, l, mid
#define rson rt << 1 | 1, mid + 1, r
#define PB push_back
#define POP pop_back
const double pi = acos(-1);
const int maxn = 1e5 + 10;
const int maxm = (maxn<<5) + 5;
const ll mod = 1e9 + 7;
const int hash_mod = 19260817;
int T, n, m, id;
vector<int> f[maxn], z[maxn];
int fa[maxn][64], du[maxn], top[maxn], h[maxn];
void topsort(){
    queue<int> que;
    for(int i = 1 ; i <= n ; ++ i){
        if(!du[i]) que.push(i);
    }
    while(!que.empty()){
        int u = que.front();
        que.pop();
        top[++id] = u;
        for(int i = 0 ; i < f[u].size() ; ++ i){
            int v = f[u][i];
            -- du[v];
            if(!du[v]) que.push(v);
        }
    }
}
void init(){
    id = 0;
    for(int i = 1 ; i <= n ; ++ i){
        z[i].clear(); f[i].clear();
        du[i] = 0; h[i] = 0;
    }
}
int lca(int x, int y){
    if(h[x] < h[y]) swap(x, y);
    int k = h[x] - h[y];
    for(int i = 31 ; i >= 0 ; -- i){
        if((k >> i) & 1) x = fa[x][i];
    }
    if(x == y) return x;
    for(int i = 31 ; i >= 0 ; -- i){
        if(fa[x][i] != fa[y][i]) x = fa[x][i], y = fa[y][i];
    }
    return fa[x][0];
}
int main()
{
    //freopen("E://one.txt","r",stdin); //輸入重定向，輸入數據將從in.txt文件中讀取
    //freopen("E://oneout.txt","w",stdout); //輸出重定向，輸出數據將保存在out.txt文件中
    int u, v, q;
    scanf("%d", &T);
    while(T --){
        scanf("%d %d", &n, &m);
        init();
        for(int i = 1 ; i <= m ; ++ i){
            scanf("%d %d", &u, &v);
            du[u] ++;
            f[v].PB(u); z[u].PB(v);
        }
        topsort();
        for(int i = 1 ; i <= n ; ++ i){
            int u = top[i];
            int x = (z[u].size() == 0 ? 0 : z[u][0]);
            for(int i = 0 ; i < z[u].size() ; ++ i){
                int v = z[u][i];
                x = lca(x, v);
            }
            h[u] = h[x] + 1;
            fa[u][0] = x;
            for(int i = 1 ; i <= 31 ; ++ i) fa[u][i] = fa[fa[u][i-1]][i-1];
        }
        scanf("%d", &q);
        while(q --){
            scanf("%d %d", &u, &v);
            cout << h[u] + h[v] - h[lca(u, v)] << endl;
        }
    }
    return 0;
}