PAT 甲级 1013. Battle Over Cities

1013. Battle Over Cities (25)

时间限制

400 ms

内存限制

65536 kB

代码长度限制

16000 B

判题程序

Standard

作者

CHEN, Yue

It is vitally important to have all the cities connected by highways in a war. If a city is occupied by the enemy, all the highways from/toward that city are closed. We must know immediately if we need to repair any other highways to keep the rest of the cities connected. Given the map of cities which have all the remaining highways marked, you are supposed to tell the number of highways need to be repaired, quickly.

For example, if we have 3 cities and 2 highways connecting city₁-city₂ and city₁-city₃. Then if city₁ is occupied by the enemy, we must have 1 highway repaired, that is the highway city₂-city₃.

Input

Each input file contains one test case. Each case starts with a line containing 3 numbers N (<1000), M and K, which are the total number of cities, the number of remaining highways, and the number of cities to be checked, respectively. Then M lines follow, each describes a highway by 2 integers, which are the numbers of the cities the highway connects. The cities are numbered from 1 to N. Finally there is a line containing K numbers, which represent the cities we concern.

Output

For each of the K cities, output in a line the number of highways need to be repaired if that city is lost.

Sample Input

3 2 31 21 31 2 3

Sample Output

100

题意：有N个城市，每个城市之间有几条通路，每次查询还有一个城市被占领，以至于被切断与其他城市的连接，求每次查询需要有建多少条路使其余城市保持畅通

就是求有多少个连通块，标准并查集

#include<bits/stdc++.h>using namespace std;int fa[1024];int Find(int a){    return a == fa[a]?fa[a]:fa[a] = Find(fa[a]);}vector<pair<int,int> > e;int main(){    int m,n,k;    scanf("%d%d%d",&n,&m,&k);    for(int i = 0;i < m;i++)    {        int a,b;        scanf("%d%d",&a,&b);        e.push_back(make_pair(a,b));    }    while(k--)    {        for(int i = 1;i <= n;i++)            fa[i] = i;        int tmp;        scanf("%d",&tmp);        for(int i = 0;i < m;i++)        {            int a = e[i].first;            int b = e[i].second;            if(a == tmp||b == tmp)                continue;            a = Find(a);            b = Find(b);            if(a != b)                fa[a] = b;        }        int ans = 0;        for(int i = 1;i <= n;i++)            if(fa[i] == i)                ans++;        printf("%d\n",ans-2);    }    return 0;}