POJ 3660 Cow Contest 最短路floyd
2015-09-22 21:39
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Cow Contest
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
Sample Output
告诉两个牛实力的排序,排在前面的实力强,问有几头牛实力是可以确定的
floyd先求出整个的连通性,对于一头牛,如果实力比他强和比他弱的牛数目和等于n-1,那么这个牛的排名是可以确定的。
Time Limit: 1000MS | Memory Limit: 65536K | |
Total Submissions: 8551 | Accepted: 4802 |
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
告诉两个牛实力的排序,排在前面的实力强,问有几头牛实力是可以确定的
floyd先求出整个的连通性,对于一头牛,如果实力比他强和比他弱的牛数目和等于n-1,那么这个牛的排名是可以确定的。
#include <iostream> #include <stdio.h> #include <string> #include <cstring> #include <algorithm> #include <cmath> using namespace std; int mp[1009][1009]; int befor[1009]; int after[1009]; int main() { int n,m; while(~scanf("%d%d",&n,&m)) { memset(mp,0,sizeof mp); memset(befor,0,sizeof befor); memset(after,0,sizeof after); int a,b; for(int i=0;i<m;i++) { scanf("%d%d",&a,&b); mp[b][a]=1; } for(int k=1;k<=n;k++) { for(int i=1;i<=n;i++) { for(int j=1;j<=n;j++) { mp[i][j]=mp[i][j] | (mp[i][k]&mp[k][j]); } } } for(int i=1;i<=n;i++) for(int j=1;j<=n;j++) { if(i==j) continue; if(mp[i][j]) { befor[i]++; after[j]++; } } int ans=0; for(int i=1;i<=n;i++) { if(befor[i]+after[i]==n-1) ans++; } printf("%d\n",ans); } return 0; }
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