Description
圆方树板子，自己看。。。

Sample Input
5 7 2
1 2
1 3
1 4
2 3
2 4
3 4
1 5
1 4
2 5

Sample Output
1
2

写这篇博客完全是为了存个板子，谢谢。

#include <vector>
#include <cstdio>
#include <cstring>
#include <algorithm>

using namespace std;
int _min(int x, int y) {
     return x < y ? x : y;}
int read() {
     
	int s = 0, f = 1; char ch = getchar();
	while(ch < '0' || ch > '9') {
     if(ch == '-') f = -1; ch = getchar();}
	while(ch >= '0' && ch <= '9') s = s * 10 + ch - '0', ch = getchar();
	return s * f;
}

struct edge {
     
	int x, y, next;
} e[3100000], e2[3100000]; int len, len2, last[110000], last2[210000];
int ll[210000], dep[210000], fa[210000][20], dis[210000];
int id, cnt, tp, sta[110000], low[110000], dfn[110000];
vector<int> q[110000];
int n, m, a[110000];

bool cmp(int x, int y) {
     return ll[x] < ll[y];}

void ins(int x, int y) {
     
	e[++len].x = x; e[len].y = y;
	e[len].next = last[x]; last[x] = len;
}

void ins2(int x, int y) {
     
	e2[++len2].x = x; e2[len2].y = y;
	e2[len2].next = last2[x]; last2[x] = len2;
}

void tarjan(int x) {
     
	dfn[x] = low[x] = ++id; sta[++tp] = x;
	for(int k = last[x]; k; k = e[k].next) {
     
		int y = e[k].y;
		if(!dfn[y]) {
     
			tarjan(y);
			low[x] = _min(low[x], low[y]);
			if(low[y] >= dfn[x]) {
     
				int i; cnt++;
				do {
     
					i = sta[tp--];
					q[cnt].push_back(i);
				} while(i != y); q[cnt].push_back(x);
			}
		} else low[x] = _min(low[x], dfn[y]);
	}
}

void dfs(int x) {
     
	ll[x] = ++id;
	dis[x] = dis[fa[x][0]] + (x > n);
	for(int i = 1; (1 << i) <= dep[x]; i++) fa[x][i] = fa[fa[x][i - 1]][i - 1];
	for(int k = last2[x]; k; k = e2[k].next) {
     
		int y = e2[k].y;
		if(y != fa[x][0]) fa[y][0] = x, dep[y] = dep[x] + 1, dfs(y);
	}
}

int LCA(int x, int y) {
     
	if(dep[x] > dep[y]) swap(x, y);
	for(int i = 18; i >= 0; i--) if(dep[y] - dep[x] >= (1 << i)){
     
		y = fa[y][i];
	} if(x == y) return x;
	for(int i = 18; i >= 0; i--) if(fa[x][i] != fa[y][i]){
     
		x = fa[x][i], y = fa[y][i];
	} return fa[x][0];
}

int main() {
     
	n = read(), m = read();
	int Q = read();
	for(int i = 1; i <= cnt; i++) q[i].clear();
	len = 0; memset(last, 0, sizeof(last));
	memset(dfn, 0, sizeof(dfn));
	memset(low, 0, sizeof(low));
	id = tp = cnt = 0;
	for(int i = 1; i <= m; i++) {
     
		int x = read(), y = read();
		ins(x, y), ins(y, x);
	} tarjan(1);
	len2 = 0; memset(last2, 0, sizeof(last2));
	for(int i = 1; i <= cnt; i++) {
     
		int o = i + n;
		for(int j = 0; j < q[i].size(); j++) {
     
			int x = q[i][j];
			ins2(o, x), ins2(x, o);
		}
	} memset(fa, 0, sizeof(fa));
	id = 0; dep[1] = dis[1] = 0; dfs(1);
	for(int i = 1; i <= Q; i++) {
     
		int x = read(), y = read();
		int lca = LCA(x, y);
		printf("%d\n", dis[x] + dis[y] - dis[lca] - dis[fa[lca][0]]);
	}
	return 0;
}