嘟嘟嘟
很久不寫樹剖，細節有點小問題。
這題比較好想。看到刪邊，通常就能想到離線加邊。
而後考慮若是一條邊是關鍵邊，那麼他必定是一個橋。所以首先要作的是邊雙縮點。
縮完點後圖就變成了樹。至於加邊，顯然就是把這條邊所在環上的點縮成了一個點。但若是再暴力縮點的話會超時。
實際上至關於把樹上在環中的邊的邊權改爲了0.而後詢問的時候就是樹上兩點間距離了。
因而上樹剖。
細節就是樹剖的時候不要改lca。這點我注意到了，關鍵是每一次我都沒有改鏈的頂端結點……ios
#include<cstdio>
#include<iostream>
#include<cmath>
#include<algorithm>
#include<cstring>
#include<cstdlib>
#include<cctype>
#include<vector>
#include<stack>
#include<queue>
#include<assert.h>
#include<map>
using namespace std;
#define enter puts("")
#define space putchar(' ')
#define Mem(a, x) memset(a, x, sizeof(a))
#define In inline
typedef long long ll;
typedef double db;
const int INF = 0x3f3f3f3f;
const db eps = 1e-8;
const int maxn = 3e4 + 5;
const int maxm = 1e5 + 5;
In ll read()
{
ll ans = 0;
char ch = getchar(), last = ' ';
while(!isdigit(ch)) last = ch, ch = getchar();
while(isdigit(ch)) ans = (ans << 1) + (ans << 3) + ch - '0', ch = getchar();
if(last == '-') ans = -ans;
return ans;
}
In void write(ll x)
{
if(x < 0) x = -x, putchar('-');
if(x >= 10) write(x / 10);
putchar(x % 10 + '0');
}
In void MYFILE()
{
#ifndef mrclr
freopen("ha.in", "r", stdin);
freopen("ha.out", "w", stdout);
#endif
}
int n, m, qcnt = 0;
struct edges {int x, y;}E[maxm];
struct Node
{
bool flg; int x, y;
}q[maxm];
map<int, int> mp[maxn];
int ans[maxm], acnt = 0;
struct Edge
{
int nxt, to;
}e[maxm << 1];
int head[maxn], ecnt = -1;
In void addEdge(int x, int y)
{
e[++ecnt] = (Edge){head[x], y};
head[x] = ecnt;
}
bool in[maxn];
int st[maxn], Top = 0;
int dfn[maxn], low[maxn], cnt = 0;
int col[maxn], ccol = 0;
In void tarjan(int now, int _e)
{
st[++Top] = now; in[now] = 1;
dfn[now] = low[now] = ++cnt;
for(int i = head[now], v; ~i; i = e[i].nxt)
{
if(!dfn[v = e[i].to])
{
tarjan(v, i);
low[now] = min(low[now], low[v]);
}
else if((i ^ 1) ^ _e) low[now] = min(low[now], dfn[v]);
}
if(dfn[now] == low[now])
{
int x; ++ccol;
do
{
x = st[Top--], in[x] = 0;
col[x] = ccol;
}while(x ^ now);
}
}
Edge e2[maxm << 1];
int head2[maxn], ecnt2 = -1;
In void addEdge2(int x, int y)
{
e2[++ecnt2] = (Edge){head2[x], y};
head2[x] = ecnt2;
}
In void buildGraph(int now)
{
int u = col[now];
for(int i = head[now], v; ~i; i = e[i].nxt)
if((v = col[e[i].to]) ^ u) addEdge2(u, v);
}
int a[maxn], siz[maxn], dep[maxn], fa[maxn], son[maxn];
In void dfs1(int now, int _f)
{
siz[now] = 1;
for(int i = head2[now], v; ~i; i = e2[i].nxt)
{
if((v = e2[i].to) == _f) continue;
a[v] = 1;
fa[v] = now, dep[v] = dep[now] + 1;
dfs1(v, now);
siz[now] += siz[v];
if(!son[now] || siz[son[now]] < siz[v]) son[now] = v;
}
}
int top[maxn], dfsx[maxn], pos[maxn];
In void dfs2(int now, int _f)
{
dfsx[now] = ++cnt, pos[cnt] = now;
if(son[now]) top[son[now]] = top[now], dfs2(son[now], now);
for(int i = head2[now], v; ~i; i = e2[i].nxt)
{
if((v = e2[i].to) == _f || v == son[now]) continue;
top[v] = v, dfs2(v, now);
}
}
int l[maxn << 2], r[maxn << 2], sum[maxn << 2], lzy[maxn << 2];
In void build(int L, int R, int now)
{
l[now] = L, r[now] = R;
lzy[now] = -1;
if(L == R) {sum[now] = a[pos[L]]; return;}
int mid = (L + R) >> 1;
build(L, mid, now << 1);
build(mid + 1, R, now << 1 | 1);
sum[now] = sum[now << 1] + sum[now << 1 | 1];
}
In void change(int now)
{
sum[now] = lzy[now] = 0;
}
In void pushdown(int now)
{
if(~lzy[now])
{
change(now << 1), change(now << 1 | 1);
lzy[now] = -1;
}
}
In void update(int L, int R, int now)
{
if(L > R) return;
if(l[now] == L && r[now] == R) {change(now); return;}
pushdown(now);
int mid = (l[now] + r[now]) >> 1;
if(R <= mid) update(L, R, now << 1);
else if(L > mid) update(L, R, now << 1 | 1);
else update(L, mid, now << 1), update(mid + 1, R, now << 1 | 1);
sum[now] = sum[now << 1] + sum[now << 1 | 1];
}
In int query(int L, int R, int now)
{
if(L > R) return 0;
if(l[now] == L && r[now] == R) return sum[now];
pushdown(now);
int mid = (l[now] + r[now]) >> 1;
if(R <= mid) return query(L, R, now << 1);
else if(L > mid) return query(L, R, now << 1 | 1);
else return query(L, mid, now << 1) + query(mid + 1, R, now << 1 | 1);
}
In void update_path(int x, int y)
{
if(x == y) return;
while(top[x] ^ top[y])
{
if(dep[top[x]] < dep[top[y]]) swap(x, y);
update(dfsx[top[x]], dfsx[x], 1);
x = fa[top[x]];
}
if(dep[x] < dep[y]) swap(x, y);
update(dfsx[y] + 1, dfsx[x], 1);
}
In int query_path(int x, int y)
{
if(x == y) return 0;
int ret = 0;
while(top[x] ^ top[y])
{
if(dep[top[x]] < dep[top[y]]) swap(x, y);
ret += query(dfsx[top[x]], dfsx[x], 1);
x = fa[top[x]];
}
if(dep[x] < dep[y]) swap(x, y);
ret += query(dfsx[y] + 1, dfsx[x], 1);
return ret;
}
int main()
{
MYFILE();
Mem(head, -1), Mem(head2, -1);
n = read(), m = read();
for(int i = 1; i <= m; ++i)
{
int x = read(), y = read();
if(x > y) swap(x, y);
E[i] = (edges){x, y};
++mp[x][y];
}
int c;
while(scanf("%d", &c) && ~c)
{
int x = read(), y = read();
if(x > y) swap(x, y);
q[++qcnt] = (Node){c, x, y};
if(!c && mp[x][y]) --mp[x][y];
}
for(int i = 1; i <= m; ++i)
{
int x = E[i].x, y = E[i].y;
if(mp[x][y]) addEdge(x, y), addEdge(y, x);
}
for(int i = 1; i <= n; ++i) if(!dfn[i]) tarjan(i, 0);
for(int i = 1; i <= n; ++i) buildGraph(i);
dfs1(1, 0), cnt = 0, top[1] = 1, dfs2(1, 0);
build(1, cnt, 1);
for(int i = qcnt; i; --i)
{
int x = q[i].x, y = q[i].y;
if(q[i].flg) ans[++acnt] = query_path(col[x], col[y]);
else update_path(col[x], col[y]);
}
for(int i = acnt; i; --i) write(ans[i]), enter;
return 0;
}