POJ 3660 Cow Contest
Time Limit: 1000MS | Memory Limit: 65536K | |
Total Submissions: 7156 | Accepted: 3957 |
Description
N (1 ≤ N ≤ 100) cows, conveniently numbered 1..N, are participating in a programming contest. As we all know, some cows code better than others. Each cow has a certain constant skill rating that is unique among the competitors.
The contest is conducted in several head-to-head rounds, each between two cows. If cow A has a greater skill level than cow B (1 ≤ A ≤ N; 1 ≤ B ≤ N; A ≠ B), then cow A will always beat cow B.
Farmer John is trying to rank the cows by skill level. Given a list the results of M (1 ≤ M ≤ 4,500) two-cow rounds, determine the number of cows whose ranks can be precisely determined from the results. It is guaranteed that the results of the rounds will not be contradictory.
Input
* Line 1: Two space-separated integers: N and M
* Lines 2..M+1: Each line contains two space-separated integers that describe the competitors and results (the first integer, A, is the winner) of a single round of competition: A and B
Output
* Line 1: A single integer representing the number of cows whose ranks can be determined
Sample Input
5 5 4 3 4 2 3 2 1 2 2 5
Sample Output
2
Source
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
#include <iostream> #include <cstdio> #include <cstring> #include <algorithm> #include <cmath> #include <vector> #include <queue> #include <map> #include <string> using namespace std; typedef long long LL; const int N = 110; const int inf = 1e7+7; int n , m , dis[N][N] , in_cnt[N] , out_cnt[N]; void init_dis() { for( int i = 0 ; i <= n ; ++i ) { for( int j = 0 ; j <= n ; ++j ) { dis[i][j] = inf ; } dis[i][i] = 0 ; } } void check_dis() { for( int i = 1 ; i <= n ; ++i ) { for( int j = 1 ; j <= n ; ++j ) if( dis[i][j] < inf )cout << dis[i][j] <<' '; else cout << "inf "; cout << endl; } } void run() { int u , v ; init_dis(); while( m-- ) { scanf("%d%d",&u,&v); dis[u][v] = 1 ; } for( int k = 1 ; k <= n ; ++k ) { for( int i = 1 ; i <= n ; ++i ) { for( int j = 1 ; j <= n ; ++j ){ dis[i][j] = min( dis[i][j] , dis[i][k] + dis[k][j] ); } } } // check_dis(); memset( in_cnt , 0 , sizeof in_cnt ); memset( out_cnt , 0 , sizeof out_cnt ); for( int i =1 ; i <= n ; ++i ) { for( int j = 1 ; j <= n ; ++j ){ if( i == j || dis[i][j] >= inf ) continue ; out_cnt[i]++ , in_cnt[j]++; } } int ans = 0 ;for( int i = 1 ; i <= n ; ++i ) if( in_cnt[i] + out_cnt[i] >= n - 1 ) ans++; printf("%d\n",ans); } int main() { #ifdef LOCAL freopen("in.txt","r",stdin); #endif // LOCAL ios::sync_with_stdio(false); while( ~scanf("%d%d",&n,&m) ) run(); }