1544. Classmates 3

http://acm.timus.ru/problem.aspx?space=1&num=1544

bfs

代码：

#include<iostream>

#include<cstdio>

#include<cstring>

#include<string>

#include<map>

#include<vector>

#include<stack>

#include<set>

#include<map>

#include<queue>

#include<deque>

#include<algorithm>

#include<cmath>

#define LL long long

//#pragma comment(linker, "/STACK:1024000000,1024000000")

using namespace std;

const int INF=0x3f3f3f3f;

const int N=105;

char p[N];

char a[N];

vector<char>vt[N];

int head[N],I;

struct node

{

    int j,next;

}edge[N*N];

void add(int i,int j)

{

    edge[I].j=j;

    edge[I].next=head[i];

    head[i]=I++;

}

bool bfs(int s,char c,int n)

{

    queue<int>qt;

    qt.push(s);

    a[s]=c;

    while(!qt.empty())

    {

        int x=qt.front();

        qt.pop();

        for(int t=head[x];t!=-1;t=edge[t].next)

        {

            int j=edge[t].j;

            if(a[j]!=c)

            {

                a[j]=c;

                qt.push(j);

            }

        }

    }

    for(int i=1;i<=n;++i)

    if(a[i]!=c)

    return false;

    return true;

}

int main()

{

    //freopen("data.in","r",stdin);

    int n,m;

    cin>>n>>m;

    memset(head,-1,sizeof(head));

    I=0;

    for(int i=1;i<=n;++i)

    vt[i].clear();

    bool flag=true;

    for(int i=1;i<=n;++i)

    {

        cin>>p[i];

        if(i>1&&p[i]!=p[i-1])

        flag=false;

    }

    if(flag)

    {cout<<"0"<<endl;return 0;}

    while(m--)

    {

        int l,r;

        cin>>l>>r;

        add(l,r);

        add(r,l);

    }

    for(int i=1;i<=n;++i)

    {

        for(int j=1;j<=n;++j)

        a[j]=p[j];

        while(!bfs(i,((a[i]=='J')?'E':'J'),n))

        vt[i].push_back(a[i]);

        vt[i].push_back(a[i]);

    }

    int k=1;

    for(int i=2;i<=n;++i)

    if(vt[i].size()<vt[k].size())

    k=i;

    cout<<vt[k].size()<<endl;

    for(unsigned int i=0;i<vt[k].size();++i)

    cout<<k<<" "<<vt[k][i]<<endl;

    return 0;

}