Revocable search board

Revocable search set is supported “ Disconnect ” The consolidation of operations , But this undo must be done in stack order .

Due to the need to implement revocation , You need to use the stack to record all the completed connection operations . And it can't compress the path .

The board is as follows ：

#include <bits/stdc++.h>
using namespace std;
#define FOR(i, a, b) for (int i = (a); i <= (b); i++)
const int N = 2e5+5;
int n,fa[N],rk[N];
struct edge{int u,v,w;} stk[N]; int top = 0; // Record the stack of operations ,u and v Are the two points of connection ,w Represents before connecting u and v Equal rank or not .top It's the top of the stack 

inline void init(){FOR(i,1,n) fa[i]=i, rk[i]=1;} // initialization 
int find(int x){return fa[x]==x ? x : find(fa[x]);} // Recursively looking for ancestors , Note that path compression is not allowed here 
bool same(int u,int v){return find(u)==find(v);} // Judge u and v Whether ancestors are equal 
void merge(int u,int v){ // Connect u and v
	u = find(u), v = find(v); // hold u and v Assigned to its own ancestor 
	if(u==v) return; // If the ancestors are the same , Do nothing 
	if(rk[u] > rk[v]) swap(u,v); // Adjust by rank u and v Father son relationship of , Xiao Lianda 
	fa[u] = v; // Connect 
	stk[++top] = {u, v, rk[u]==rk[v]}; // Record the connection in the stack 
	if(rk[u]==rk[v]) rk[v]++; // If equal rank ,v The rank of +1
}
void undone(){ // Undo the last connection 
	int u = stk[top].u, v = stk[top].v, w = stk[top].w;
	rk[v] -= w; // If the rank before connection is equal , So now v The rank of -1
	fa[u] = u; // Cancel u,v Connection between 
	top--;
}