2014 UESTC Training for Graph Theory C

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求割顶，每个割顶可以将联通分量数量+1
如果割顶数目小于K,那么注意多余的点是不能增加联通分量的

另外注意dfs的第一个点要特殊处理一下

#include <map>#include <set>#include <list>#include <cmath>#include<cctype>#include <ctime>#include <deque>#include <stack>#include <queue>#include <cstdio>#include <string>#include <vector>#include <cstdlib>#include <cstring>#include <iostream>#include <algorithm>#define LL long long#define PI 3.1415926535897932626using namespace std;int gcd(int a, int b){return a % b == 0 ? b : gcd(b, a % b);}int N,M,K;#define MAXN 10003int pre[MAXN],dfs_clock,bcc_cnt;vector<int > G[MAXN];bool used[MAXN];int base;struct node{    int id;//缂栧彿    int iscut;//鍒嗗壊鎴愬嚑鍧?    friend bool operator < (const node &a,const node &b)    {        if (a.iscut==b.iscut) return a.id<b.id;        return a.iscut>b.iscut;    }}src[MAXN];void read(){    int a,b;    memset(used,0,sizeof(used));    for (int i=0;i<=N;i++) G[i].clear();    for (int i=0;i<M;i++)    {        scanf("%d%d",&a,&b);        G[a].push_back(b);        G[b].push_back(a);    }}int dfs(int u,int fa){    int lowu=pre[u]=++dfs_clock;    int child=0;    for (int i=0;i<(int)G[u].size();i++)    {        int v=G[u][i];        if (!pre[v])        {            child++;            int lowv=dfs(v,u);            lowu=min(lowu,lowv);            if (lowv>=pre[u])            {                src[u].iscut++;                bcc_cnt++;            }        }        else if (pre[v]<pre[u] && v!=fa)        {            lowu=min(lowu,pre[v]);        }    }    if (fa<0 && child==1)src[u].iscut=0;    return lowu;}void find(){    memset(pre,0,sizeof(pre));    for (int i=0;i<N;i++)    {        src[i].id=i;        src[i].iscut=0;    }    //memset(bccno,0,sizeof(bccno));    dfs_clock=bcc_cnt=0;    for (int i=0;i<N;i++)        if (!pre[i]) {base++;dfs(i,-1);}}int main(){    //freopen("sample.txt","r",stdin);    while (scanf("%d%d%d",&N,&M,&K)!=EOF)    {        base=0;        read();        find();        int cas=0;        if (src[0].iscut>0) src[0].iscut--;        sort(src,src+N);        //printf("%d\n",bcc_cnt);        for (int i=0;i<K;i++)           {             //  if (src[i].iscut==0) break;             printf("%d %d\n",src[i].id,src[i].iscut+base);             used[src[i].id]=true;             cas++;           }        putchar('\n');    }    return 0;}

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