HDU-4324 Triangle Love (topological sort)

https://vjudge.net/problem/HDU-4324

Test instructions

Each group of data a n represents n individuals, and then the matrix of N*n represents the relationship between these people, input must be satisfied if a does not like B then B must like a, and will not appear a and b mutually like the situation, ask you whether there is a triangle love.

Analysis

is to ask if there is a ternary ring. To determine whether a graph exists in a loop, you can use topological ordering, and the sorting fails with a loop. So how to judge the existence of the ring is ternary ring it?

Suppose there is an n-ary ring, and there is such an adjacent three element x--"y--" Z on the ring. If it is z--x, then there is ternary ring, otherwise, there will be x--"Z, then you can ignore the Y, it becomes the n-1 yuan ring. In this way, there must be a ternary ring. Therefore, the problem is to ask whether there is a ring.

#include <iostream>#include<cmath>#include<cstring>#include<queue>#include<vector>#include<cstdio>#include<algorithm>#include<map>#include<Set>#include<bitset>#defineRep (i,e) for (int i=0;i< (e); i++)#defineREP1 (i,e) for (int i=1;i<= (e); i++)#defineREPX (i,x,e) for (int i= (x); i<= (e); i++)#defineX First#defineY Second#definePB push_back#defineMP Make_pair#defineMset (Var,val) memset (Var,val,sizeof (VAR))#defineSCD (a) scanf ("%d", &a)#defineSCDD (A, b) scanf ("%d%d", &a,&b)#defineSCDDD (a,b,c) scanf ("%d%d%d", &a,&b,&c)#definePD (a) printf ("%d\n", a)#defineSCL (a) scanf ("%lld", &a)#defineSCLL (A, b) scanf ("%lld%lld", &a,&b)#defineSclll (a,b,c) scanf ("%lld%lld%lld", &a,&b,&c)#defineIOS Ios::sync_with_stdio (false); Cin.tie (0)using namespaceStd;typedefLong Longll;template<classT>voidTest (T a) {cout<<a<<Endl;} Template<classTclassT2>voidTest (T a,t2 b) {cout<<a<<" "<<b<<Endl;} Template<classTclassT2,classT3>voidTest (T a,t2 b,t3 c) {cout<<a<<" "<<b<<" "<<c<<Endl;}Const intN = 1e6+Ten;//const int MAXN =;Const intINF =0x3f3f3f3f;Constll INF =0x3f3f3f3f3f3f3f3fll;Constll mod =1000000007;intT;voidtestcase () {printf ("Case #%d:",++T);}Const intMAXN =2500;Const intMAXM = -;CharMA[MAXN];int inch[MAXN];intHEAD[MAXN], CNT;intN, K;structNode {intu, V, next;}; Node EDGE[MAXN*MAXN];voidinit () {CNT=0; memset (Head,-1,sizeof(head)); memset (inch,0,sizeof(inch));}voidAddintUintv) {edge[cnt]={u, V, Head[u]}; Head[u]= cnt++;}voidTopu () {testcase (); Queue<int>Q; intans=0;  for(intI=0; i<n;++i) {        if(!inch[i])            {Q.push (i); Ans++; }    }     while(!Q.empty ()) {        intu=Q.front ();        Q.pop ();  for(inti=head[u];i!=-1; i=Edge[i].next) {            intv=edge[i].v; inch[v]--; if(!inch[v])                {Q.push (v); Ans++; }        }    }    if(n==ans) printf ("no\n"); Elseprintf ("yes\n");}intMain () {#ifdef LOCAL freopen ("In.txt","R", stdin);#endif //LOCAL    intT; scanf ("%d", &t); T=0;  while(t--) {init (); scanf ("%d", &N);  for(inti =0; I < n; ++i)            {gets (MA);  for(intj =0; J < N; ++j)if(Ma[j] = ='1') {Add (I, j); inch[j]++;    }} topu (); }    return 0;}

HDU-4324 Triangle Love (topological sort)