Luogu2783 有机化学之神偶尔会做作弊 （树链剖分，缩点）

当联通块size<=2时不管

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#define R(a,b,c) for(register int  a = (b); a <= (c); ++ a)
#define nR(a,b,c) for(register int  a = (b); a >= (c); -- a)
#define Max(a,b) ((a) > (b) ? (a) : (b))
#define Min(a,b) ((a) < (b) ? (a) : (b))
#define Fill(a,b) memset(a, b, sizeof(a))
#define Abs(a) ((a) < 0 ? -(a) : (a))
#define Swap(a,b) a^=b^=a^=b
#define ll long long

#define ON_DEBUG

#ifdef ON_DEBUG

#define D_e_Line printf("\n\n----------\n\n")
#define D_e(x)  cout << #x << " = " << x << endl
#define Pause() system("pause")
#define FileOpen() freopen("in.txt","r",stdin);

#else

#define D_e_Line ;
#define D_e(x)  ;
#define Pause() ;
#define FileOpen() ;

#endif

struct ios{
    template<typename ATP>ios& operator >> (ATP &x){
        x = 0; int f = 1; char c;
        for(c = getchar(); c < '0' || c > '9'; c = getchar()) if(c == '-')  f = -1;
        while(c >= '0' && c <= '9') x = x * 10 + (c ^ '0'), c = getchar();
        x*= f;
        return *this;
    }
}io;
using namespace std;

const int N = 10007;
const int M = 50007;

int n, m;
struct Edge{
	int nxt, pre, from;
}e[M << 1], e2[M << 1];
int head[N], head2[N], cntEdge, cntEdge2;
inline void add(int u, int v){
	e[++cntEdge] = (Edge){head[u], v, u}, head[u] = cntEdge;
}
inline void add2(int u, int v){
	e2[++cntEdge2] = (Edge){head2[u], v}, head2[u] = cntEdge2; // !
}

namespace Tarjan{
int dfn[N], dfnIndex, low[N], vis[N];
int sta[N], top;
int scc[N], sccIndex;
inline void Tarjan(int u, int fa){
	dfn[u] = low[u] = ++dfnIndex;
	sta[++top] = u;
	vis[u] = true;
	for(register int i = head[u]; i; i = e[i].nxt){
		int v = e[i].pre;
		if(v == fa) continue; // size <= 2
		if(!dfn[v]){
			Tarjan(v, u);
			low[u] = Min(low[u], low[v]);
		}
		else if(vis[v]){
			low[u] = Min(low[u], dfn[v]);
		}
	}
	if(dfn[u] == low[u]){
		++sccIndex;
		do{
			vis[sta[top]] = false;
			scc[sta[top]] = sccIndex;
		}while(sta[top--] != u); // !
	}
}
inline void Rebuild(){
	R(i,1,cntEdge){
		if(scc[e[i].pre] != scc[e[i].from]){
			add2(scc[e[i].from], scc[e[i].pre]); //!
		}

	}
}
}

namespace Tree{ // ! e, e2
int dep[N], fa[N], son[N], siz[N];
inline void DFS_First(int u, int father){
	dep[u] = dep[father] + 1, fa[u] = father, siz[u] = 1;
	for(register int i = head2[u]; i; i = e2[i].nxt){
		int v = e2[i].pre;
		if(v == father) continue;
		DFS_First(v, u);
		siz[u] += siz[v];
		if(!son[u] || siz[v] > siz[son[u]]){
			son[u] = v;
		}
	}
}
int dfn[N], dfnIndex, top[N];
inline void DFS_Second(int u, int ancester){
	dfn[u] = ++dfnIndex, top[u] = ancester;
	if(!son[u]) return;
	DFS_Second(son[u], ancester);
	for(register int i = head2[u]; i; i = e2[i].nxt){
		int v = e2[i].pre;
		if(v != son[u] && v != fa[u]){
			DFS_Second(v, v);
		}
	}
}
inline int Query(int x, int y){
	int sum = 0;
	while(top[x] != top[y]){
		if(dep[top[x]] < dep[top[y]]) Swap(x, y);
		sum += dep[x] - dep[top[x]] + 1;
		x = fa[top[x]];
	}
	if(dep[x] < dep[y]) Swap(x, y);
	return sum + dep[x] - dep[y] + 1;
}
}

inline string Calc(int x){
	string ans = "";
	while(x){
		ans += (x & 1) ? "1" : "0";
		x >>= 1;
	}
	return ans;
}
int main(){
	io >> n >> m;
	R(i,1,m){
		int u, v;
		io >> u >> v;
		add(u, v);
		add(v, u);
	}

	R(i,1,n){
		if(!Tarjan::dfn[i]){
			Tarjan::Tarjan(i ,0);
		}
	}

	Tarjan::Rebuild();

	Tree::DFS_First(1, 0);
	Tree::DFS_Second(1, 1);

	int Ques;
	io >> Ques;
	while(Ques--){
		int x, y;
		io >> x >> y;
		string ans = Calc(Tree::Query(Tarjan::scc[x], Tarjan::scc[y]));
		int len = ans.size();
		nR(i,len - 1, 0){
			cout << ans[i];
		}
		putchar('\n');
	}
	return 0;
}