并查集

题目：http://poj.org/problem?id=1182

为每个动物创建三个元素i-A，i-B，i-C，并利用这3*N个元素建立并查集。

参考挑战程序设计书

#include <iostream>#include <cstdio>#include <algorithm>#include <cstring>using namespace std;#define maxn 100009int N, K;int par[maxn*3], rankx[maxn*3];int T[maxn], X[maxn], Y[maxn];void init(int n){    for(int i=0;i<n;i++)    {        par[i]=i;        rankx[i]=0;    }}int find(int x){    if(par[x]==x)     return x;     else{        return par[x] = find(par[x]);     }}void unite(int x, int y){    x = find(x);    y = find(y);    if(x == y)      return ;    if(rankx[x] < rankx[y])    {        par[x]=y;    }else{       par[y]=x;       if(rankx[x]==rankx[y])        rankx[x]++;    }}bool same(int x, int y){    return find(x)==find(y);}int main(){    scanf("%d%d", &N,&K);    init(N*3);    int ans=0, x, y, t;    for(int i=0;i<K;i++)    {        scanf("%d %d %d", &T[i],&X[i], &Y[i]);        int t = T[i];        int x = X[i] - 1, y = Y[i] - 1;        if(x <0 ||N <= x || y  <0||N<=y){            ans++;            continue;        }        if(t==1)        {            if(same(x, y + N)||same(x, y+2*N)){                ans++;            }            else            {                unite(x, y);                unite(x+N, y+N);                unite(x+N*2, y+N*2);            }        }        else        {            if(same(x, y) || same(x, y + 2 *N)){                ans++;            }            else            {                unite(x, y+N);                unite(x+N, y+2*N);                unite(x+2*N, y);            }        }    }    printf("%d\n", ans);    return 0;}