湖南多校对抗赛（2015.05.03）Problem B: War

并查集。从后往前加边。

#include<stdio.h>
#include<string.h>
#include<math.h>
#include<algorithm>
using namespace std;
const int maxn = 1000000 + 10;
int father[maxn], u[maxn], v[maxn], Q, q[maxn], ans[maxn], ff[maxn];
int find(int x)
{
    if (x != father[x]) father[x] = find(father[x]);
    return father[x];
}
int main()
{
    int n, m, i;
    while (~scanf("%d%d", &n, &m))
    {
        memset(ff, 0, sizeof(ff));
        for (i = 0; i <= n; i++) father[i] = i;
        for (i = 1; i <= m; i++) scanf("%d%d", &u[i], &v[i]);
        scanf("%d", &Q);
        for (i = 1; i <= Q; i++){ scanf("%d", &q[i]); ff[q[i]] = 1; }
        int tot = n;//没有边的时候有n个集合
        for (i = 1; i <= m; i++)
        {
            if (ff[i] == 0)
            {
                int uf, vf;
                uf = find(u[i]);
                vf = find(v[i]);
                if (vf != uf)
                {
                    father[vf] = uf;
                    tot--; //加入一条边，集合少一个
                }
            }
        }
        ans[1] = tot;
        int j = 2;
        for (i = Q; i > 1; i--)
        {
            int uf, vf;
            uf = find(u[q[i]]);
            vf = find(v[q[i]]);
            if (vf != uf)
            {
                father[vf] = uf;
                tot--; //加入一条边，集合少一个
            }
            ans[j] = tot; j++;
        }
        for (i = Q; i >= 1; i--)
        {
            if (i > 1) printf("%d ", ans[i]);
            else printf("%d
", ans[i]);
        }
    }
    return 0;
}