pku 2492 A Bug's Life

//方法1，思路更清晰
#include <stdio.h>
#include <string.h>

#define MAXN 2005

int father[MAXN],diff[MAXN];

int find(int x)
{
    int i,t;
    for(i=x; father[i]>0; i=father[i]) ;
    while(x!=i)
    {
        t=father[x];
        father[x]=i;
        x=t;
    }
    return i;
}

int merge(int x,int y)
{
    if(x==-1) return y;
    if(y==-1) return x;
    int fx=find(x),fy=find(y);
    if(fx==fy) return fx;
    if(father[fx]>father[fy])
    {
        father[fy]+=father[fx];
        return father[fx]=fy;
    }
    else
    {
        father[fx]+=father[fy];
        return father[fy]=fx;
    }
}

inline void divide(int i,int j)
{
    int fi=find(i),fj=find(j);
    int x=merge(fi,diff[fj]);
    int y=merge(diff[fi],fj);
    //x,y都是根，diff[]总是对根进行处理
    diff[x]=y;
    diff[y]=x;
}

int main()
{
    int T,cas;
    scanf("%d",&T);
    for(cas=1; cas<=T; cas++)
    {
        int N,M,i,j;
        scanf("%d %d",&N,&M);
        getchar();
        memset(father,-1,sizeof(*father)*(N+1));
        memset(diff,-1,sizeof(*diff)*(N+1));
        bool ok=true;
        while(M--)
        {
            scanf("%d %d",&i,&j);
            if(find(i)==find(j)) ok=false;
            if(ok) divide(i,j);
        }
        if(cas>1) printf("\n");
        printf("Scenario #%d:\n",cas);
        if(ok) printf("No suspicious bugs found!\n");
        else printf("Suspicious bugs found!\n");
    }
    return 0;
}

//******************************************************************
//方法2:

#include <stdio.h>
#include <string.h>

#define MAXN 2001

int father[MAXN],oppo[MAXN];

int find(int x)
{
    int i,t;
    for(i=x; father[i]>0; i=father[i]) ;
    while(x!=i)
    {
        t=father[x];
        father[x]=i;
        x=t;
    }
    return i;
}
void merge(int x,int y)
{
    int fx=find(x),fy=find(y);
    if(fx == fy) return;
//   father[fy] = fx;
    if( father[fx] > father[fy] )
    {
        father[fy] += father[fx];
        father[fx] = fy;
    }
    else
    {
        father[fx] += father[fy];
        father[fy] = fx;
    }
}
int main()
{
    int T,cas,n,m,i,j;
    scanf("%d",&T);
    for(cas=1; cas<=T; cas++)
    {
        scanf("%d %d",&n,&m);
        memset(father,-1,sizeof(father));
        memset(oppo,-1,sizeof(oppo));
        bool ok=true;
        while(m--)
        {
            scanf("%d %d",&i,&j);
            if(find(i) == find(j)) ok=false;
            if(ok)
            {
                if(oppo[i] == -1) oppo[i]=j;
                else if(oppo[i] != j)
                {
                    merge( oppo[i], j );
                }
                if(oppo[j] == -1) oppo[j]=i;
                else if(oppo[j] != i)
                {
                    merge( oppo[j] ,i );
                }
            }
        }
        if(cas>1) printf("\n");
        printf("Scenario #%d:\n",cas);
        if(ok) printf("No suspicious bugs found!\n");
        else printf("Suspicious bugs found!\n");
    }
    return 0;
}