POJ 1703 Find them, Catch them

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原文链接：http://www.cnblogs.com/tom987690183/p/3160926.html

本文详细介绍了并查集算法在解决特定类型问题中的应用。通过一个警察与罪犯的案例，展示了如何使用并查集来判断两个元素是否属于同一集合，并提供了一段完整的C语言实现代码。

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Find them, Catch them

Time Limit: 1000MS		Memory Limit: 10000K
Total Submissions: 24739		Accepted: 7435

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

Sample Output

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

Source

POJ Monthly--2004.07.18

并查集

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
int f[100003];
int rank[100003];
void makeini(int n)
{
    int i;
    for(i=1;i<=n;i++)
    {
        rank[i]=0;
        f[i]=i;
    }
}
int find(int x)
{
    int t;
    if(x==f[x])
        return x;
    t=find(f[x]);
    rank[x]=(rank[x]+rank[f[x]])%2;
    f[x]=t;
    return t;
}
void Union(int x,int y)
{
    int x1,y1;
    x1=find(x);
    y1=find(y);
    if(x1==y1)
        return ;
    else
    {
        f[x1]=y1;
        rank[x1]=(rank[x]+rank[y]+1)%2;
    }
}
int main()
{
    int t,i,n,m,x,y,x1,y1;
    char c[5];
    scanf("%d",&t);
    {
        while(t--)
        {
            scanf("%d%d",&n,&m);
            makeini(n);
            for(i=1;i<=m;i++)
            {
                scanf("%s%d%d",c,&x,&y);
                if(c[0]=='A')
                {
                    x1=find(x);
                    y1=find(y);
                    if(x1==y1)
                    {
                        if(rank[x]==rank[y])
                            printf("In the same gang.\n");
                        else printf("In different gangs.\n");
                    }
                    else printf("Not sure yet.\n");
                }
                if(c[0]=='D')
                {
                    Union(x,y);
                }
            }
        }
    }
    return 0;
}

转载于:https://www.cnblogs.com/tom987690183/p/3160926.html