noj火烧赤壁2

这是我的一个学长出的题就是并查集但是开始没想到还能这样倒着来总之很有想法的一道题

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<vector>
using namespace std;
vector<int>tt[200005];
int b[200005];
int cc[200005][2];
int dd[200005];
int xx[200005];
int yy[200005];
int find(int x)
{
    if(b[x] != x)
        b[x] = find(b[x]);
    return (b[x]);
}
void un(int x, int y)
{
    if(find(x) != find(y))
        b[x] = y;
}
int main()
{
    int n, m;
    while(~scanf("%d%d", &n, &m))
    {
        for(int i = 0; i < n; i ++)
        {
            tt[i].clear();
        }
        memset(xx, 0, sizeof(xx));
        for(int i = 1; i <= n; i++)
        {
            b[i] = i;
        }
        for(int i = 0; i < m; i++)
        {
 
            scanf("%d%d", &cc[i][0], &cc[i][1]);
            tt[cc[i][1]].push_back(cc[i][0]);
            tt[cc[i][0]].push_back(cc[i][1]);
        }
        int t;
        scanf("%d", &t);
        int num = n - t;
        for(int i = 0; i < t ; i++)
        {
            scanf("%d", &dd[i]);
            xx[dd[i]] = 1;
        }
        for(int i = 0; i < m; i++)
        {
            if(!(xx[cc[i][0]] || xx[cc[i][1]]))
            {
                if(find(cc[i][0]) != find(cc[i][1]))
                {
                    un(find(cc[i][0]), find(cc[i][1]));
                    num--;
                }
            }
        }
        
        yy[t] = num;
        for(int i = t-1; i >= 0; i--)
        {
            xx[dd[i]] = 0;
            num++;
            for(int j = 0; j < tt[dd[i]].size(); j++)
            {
                    if(!xx[tt[dd[i]][j]])
                    {
                        if(find(dd[i]) != find(tt[dd[i]][j]))
                        {
                            un(find(tt[dd[i]][j]), find(dd[i]));
                            num--;
                        }
                    }
            }
            yy[i] = num;
        }//printf("erwsrwer\n");
        for(int i = 0; i <= t; i++)
        {
            printf("%d\n", yy[i]);
        }

    }
    return 0;
}