并查集初学（2）LA 3644 & LA3027

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1、LA 3644

题目：http://acm.hust.edu.cn:8080/judge/problem/viewProblem.action?id=12648

并查集入门题，寻找是否存在环，若存在，则cnt++

#include <cstdio>#include <cstring>#include <iostream>#include <algorithm>const int maxn=100010;using namespace std;int p[maxn];//带路径压缩的并查集int Find(int x){return p[x] == x?x:p[x]=Find(p[x]);}int main(){    int x,y;    while (scanf("%d",&x) == 1)    {        for (int i=0;i<maxn;i++) p[i]=i;        int cnt=0;        while (x != -1)        {            scanf("%d",&y);            x=Find(x);            y=Find(y);            if (x == y) cnt++;            else p[x]=y;            scanf("%d",&x);        }        printf("%d\n",cnt);    }    return 0;}

2、LA 3027

题目：http://acm.hust.edu.cn/vjudge/problem/viewProblem.action?id=33982

分析：一边路径压缩，一边维护d[i] : 结点i到树根的距离

#include <cstdio>#include <cstring>#include <iostream>#include <algorithm>using namespace std;const int maxn=20010;int p[maxn];int d[maxn];int Find(int x){    if (p[x] != x)    {        int root=Find(p[x]);        d[x] += d[p[x]];        return p[x]=root;    }    else return x;}int main(){    int T;    scanf("%d",&T);    while (T--)    {        int n,u,v;        char cmd[9];        scanf("%d",&n);        for (int i=1;i<=n;i++)        {            p[i]=i;            d[i]=0;        }        while (scanf("%s",cmd) && cmd[0] != 'O')        {            if (cmd[0] == 'I')            {                scanf("%d%d",&u,&v);                p[u]=v;                d[u]=abs(u-v) % 1000;            }            if (cmd[0] == 'E')            {                scanf("%d",&u);                int t=Find(u);                printf("%d\n",d[u]);            }        }    }    return 0;}

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