Find them, Catch them

Find them, Catch them
Time Limit: 1000MS Memory Limit: 10000K
Total Submissions: 36488 Accepted: 11188

Description
The police office in Tadu City decides to say ends to the chaos, as launch actions to root up the TWO gangs in the city, Gang Dragon and Gang Snake. However, the police first needs to identify which gang a criminal belongs to. The present question is, given two criminals; do they belong to a same clan? You must give your judgment based on incomplete information. (Since the gangsters are always acting secretly.)

Assume N (N <= 10^5) criminals are currently in Tadu City, numbered from 1 to N. And of course, at least one of them belongs to Gang Dragon, and the same for Gang Snake. You will be given M (M <= 10^5) messages in sequence, which are in the following two kinds:

1. D [a] [b]
   where [a] and [b] are the numbers of two criminals, and they belong to different gangs.

2. A [a] [b]
   where [a] and [b] are the numbers of two criminals. This requires you to decide whether a and b belong to a same gang.

Input
The first line of the input contains a single integer T (1 <= T <= 20), the number of test cases. Then T cases follow. Each test case begins with a line with two integers N and M, followed by M lines each containing one message as described above.

Output
For each message “A [a] [b]” in each case, your program should give the judgment based on the information got before. The answers might be one of “In the same gang.”, “In different gangs.” and “Not sure yet.”

Sample Input

1
5 5
A 1 2
D 1 2
A 1 2
D 2 4
A 1 4

Sample Output

Not sure yet.
In different gangs.
In the same gang.

Source
POJ Monthly–2004.07.18
题意:有两个犯罪团伙,D 操作就是表明两个人不是同一伙,A 查询两个人的关系

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <algorithm>
#define LL long long
using namespace std;

const int MAX = 110000;

struct node
{
    int pre;
    int rea;
}a[MAX];

int n,m;

void init()
{
    for(int i=0;i<=n;i++)
    {
        a[i].pre=i;
        a[i].rea=0;
    }
}

int Find(int x)
{
    if(a[x].pre==x)
    {
        return  x;
    }
    int tmp=a[x].pre;
    a[x].pre=Find(tmp);
    a[x].rea=(a[tmp].rea+a[x].rea)%2;
    return a[x].pre;
}

void Join(int x,int y,int b,int c)
{
    if(b!=c)
    {
        a[b].pre=c;
        a[b].rea=(1+a[x].rea+2-a[y].rea)%2;
    }
}
int main()
{
    int T;
    char s[10];
    scanf("%d",&T);
    while(T--)
    {
        scanf("%d %d",&n,&m);
        init();
        int u,v;
        for(int i=0;i<m;i++)
        {
            scanf("%s %d %d",s,&u,&v);
            int b=Find(u);
            int c=Find(v);
            if(s[0]=='D')
            {
                Join(u,v,b,c);
            }
            else
            {
                if(b!=c)
                {
                    printf("Not sure yet.
");
                }
                else
                {
                    if(a[u].rea==a[v].rea)
                    {
                        printf("In the same gang.
");
                    }
                    else
                    {
                        printf("In different gangs.
");
                    }
                }
            }
        }

    }
    return 0;
}