【POJ】1703 Find them, Catch them 并查集

Find them, Catch them

poj 1703 http://poj.org/problem?id=1703

Time Limit: 1000MS Memory Limit: 10000K Total

Submissions: 43420 Accepted: 13356

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:

D [a] [b]

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

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.

题解

用一个val[]记录元素在集合中的类型，考察了对并查集压缩路径的过程。

//对并查集还不了解的可以看我上一篇文章，可以借那个题理解理解http://blog.csdn.net/ctsas/article/details/54647581

由于类型只有两种，就用bool val[]了。

#include<stdio.h>
#define MAX_N 100005
int par[MAX_N];bool val[MAX_N];

void init(int n){
for(int i=0;i<=n;i++) par[i]=i,val[i]=false;
}
int find(int x){
if(par[x]==x) return x;

int t=find(par[x]);
val[x]=val[par[x]]?!val[x]:val[x];
return par[x]=t;
}
void unite(int x,int y){
int a=find(x);
int b=find(y);
val[b]=val[y]==val[b]?!val[x]:val[x];
par[b]=a;
}

int main()
{
int T,n,m,x,y;char op[2];
scanf("%d",&T);
while(T--){
scanf("%d%d",&n,&m);
init(n);
while(m--){
scanf("%s%d%d",op,&x,&y);
if(*op=='A'){
if(find(x)!=find(y)) puts("Not sure yet.");
else puts(val[x]==val[y]?"In the same gang.":"In different gangs.");
}
else unite(x,y);
}
}
return 0;
}

e786