HDOJ 5222 Exploration

题意：一个迷宫中，有n条无向隧道和m条有向隧道，每条隧道走过之后就会坍塌，不能再走，求是否存在从某一点出发能回到原点的情况。

链接：http://acm.hdu.edu.cn/showproblem.php?pid=5222

思路：对于无向图部分，通过并查集进行缩点，用缩点后的图进行有向图的判环（拓扑/强联通）

注意点：无

以下为AC代码：

Run IDSubmit TimeJudge StatusPro.IDExe.TimeExe.MemoryCode Len.LanguageAuthor136256212015-05-04 22:39:38Accepted52228470MS22208K4811 BC++luminous11

/* ************************************************# @Author  : Luminous11 ([e-mail])*# @Date    : 2015-05-02 15:32:28*# @Link    : http://blog.csdn.net/luminous11*********************************************** */#include <algorithm>#include <iostream>#include <climits>#include <iomanip>#include <cstdlib>#include <cstring>#include <cctype>#include <cstdio>#include <string>#include <vector>#include <queue>#include <stack>#include <cmath>#include <ctime>#include <deque>#include <list>#include <map>#include <set>//#include <unordered_map>//#include <unordered_set>#define pb push_back#define ll long long#define ull unsigned long long#define all(x) (x).begin(), (x).end()#define READ(f) freopen(f, "r", stdin)#define WRITE(f) freopen(f, "w", stdout)#define clr(a, v) memset( a , v , sizeof(a) )#define RS(s) scanf ( "%s", s )#define RDI(a) scanf ( "%d", &a )#define RDII(a, b) scanf ( "%d%d", &a, &b )#define RDIII(a, b, c) scanf ( "%d%d%d", &a, &b, &c )#define PL() printf ( "\n" )#define PI(a) printf ( "%d", a )#define PIL(a) printf ( "%d\n", a )#define PSL(s) printf ( "%s\n", s )#define PII(a,b) printf ( "%d %d", a, b )#define PIIL(a,b) printf ( "%d %d\n", a, b )#define PIII(a,b,c) printf ( "%d %d %d", a, b, c )#define PIIIL(a,b,c) printf ( "%d %d %d\n", a, b, c )#define rep(i,m,n) for ( int i = m; i <  n; i ++ )#define REP(i,m,n) for ( int i = m; i <= n; i ++ )#define dep(i,m,n) for ( int i = m; i >  n; i -- )#define DEP(i,m,n) for ( int i = m; i >= n; i -- )#define repi(i,m,n,k) for ( int i = m; i <  n; i += k )#define REPI(i,m,n,k) for ( int i = m; i <= n; i += k )#define depi(i,m,n,k) for ( int i = m; i >  n; i += k )#define DEPI(i,m,n,k) for ( int i = m; i >= n; i -= k )#pragma comment ( linker, "/STACK:1024000000,1024000000" )using namespace std;template <class T>inline bool RD ( T &ret ){    char c;    int sgn;    if ( c = getchar(), c ==EOF )return 0; //EOF    while ( c != '-' && ( c < '0' || c > '9' ) ) c = getchar();    sgn = ( c == '-' ) ? -1 : 1;    ret = ( c == '-' ) ? 0 : ( c - '0' );    while ( c = getchar() , c >= '0' && c <= '9' ) ret = ret * 10 + ( c - '0' );    ret *= sgn;    return 1;}inline void PD ( int x ){    if ( x > 9 ) PD ( x / 10 );    putchar ( x % 10 + '0' );}const double eps = 1e-10;const double pi = acos(-1.0);const int dir[4][2] = { 1,0, -1,0, 0,1, 0,-1 };struct node{    int x, y, cnt;    node(){}    node( int _x, int _y ) : x(_x), y(_y) {}    node( int _x, int _y, int _cnt ) : x(_x), y(_y), cnt(_cnt) {}};struct edge{    int next, to;    edge(){}};edge g[1000005];int head[1000005];int fa[1000005];int id[1000005];int tot;bool flag = 0;int point;int n, m1, m2;void init(){    tot = 0;    flag = 0;    point = 0;    memset ( id, 0, sizeof ( id ) );    memset ( head, -1, sizeof ( head ) );    for ( int i = 0; i < 1000005; i ++ )fa[i] = i;}int find ( int x ){    if ( x == fa[x] ){        return x;    }    else{        fa[x] = find ( fa[x] );        return fa[x];    }}void merge ( int u, int v ){    int x = find ( u );    int y = find ( v );    if ( x == y ){        flag = 1;        return;    }    else{        fa[x] = y;        return;    }}void addedge ( int u, int v ){    g[tot].next = head[u];    g[tot].to = v;    head[u] = tot ++;}void topo(){    int be;    vector<int> q;    for ( int i = 1; i <= n; i ++ ){        if ( id[i] == 0 ){            q.push_back ( i );        }    }    for ( int i = 0; i < q.size(); i ++ ){        int be = q[i];        for ( int j = head[be]; j != -1; j = g[j].next ){            id[g[j].to] --;            if ( id[g[j].to] == 0 )                q.push_back ( g[j].to );        }    }    int ans = q.size();    if ( ans != n )flag = 1;    return;}int main(){    int T;    scanf ( "%d", &T );    while ( T -- ){        init();        scanf ( "%d%d%d", &n, &m1, &m2 );        int u, v;        for ( int i = 0; i < m1; i ++ ){            RD ( u ); RD ( v );//scanf ( "%d%d", &u, &v );            if ( flag )continue;            merge ( u, v );        }        for ( int i = 0; i < m2; i ++ ){            RD ( u );RD ( v );//scanf ( "%d%d", &u, &v );            if ( flag )continue;            int x = find ( u );            int y = find ( v );            if ( x == y )flag = 1;            addedge ( x, y );            id[y] ++;        }        if ( flag == 0 ){            topo();        }        if ( flag ){            printf ( "YES\n" );        }        else{            printf ( "NO\n" );        }    }    return 0;}