HDU 1272(并查集求无向图环)

来源：互联网发布：java界面设计关闭编辑：程序博客网时间：2024/05/16 07:23
#include <iostream>#include <cstring>using namespace std;int set[100001];int sum;int _max;/*int Find(int i){    return set[i] == 0 ? i : (set[i] = Find(set[i]));}*/int Find(int i){    while (set[i] > 0)        i = set[i];    return i;}inline void Union(int son, int father){    int s = Find(son), f = Find(father);    if (set[s] < set[f])    {        set[s] += set[f];        set[f] = s;        if (-set[s] > _max)            _max = -set[s];    }    else    {        set[f] += set[s];        set[s] = f;        if (-set[f] > _max)            _max = -set[f];    }}int main(){    int a, b;    int _a, _b;    bool ok;    while (cin >> a >> b, ~a || ~b)    {        ok = true;        sum = 0, _max = 1;        if (!(a || b))         {            cout << "Yes" << endl;            continue;        }        memset(set, -1, sizeof(set));        if (a == b)        {            ok = false;        }        else        {            sum = 2;            Union(a, b);        }        while (cin >> a >> b, a || b)        {            if (a == b)            {                ok = false;            }            _a = Find(a), _b = Find(b);            if (_a == _b || !ok)            {                ok = false;                while (cin >> a >> b, a || b);                break;            }            else            {                if (set[a] == -1)                    ++sum;                if (set[b] == -1)                    ++sum;                Union(_a, _b);            }        }        if (ok && sum == _max)            cout << "Yes" << endl;        else cout << "No" << endl;    }}
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