POJ 2912 Rochambeau 解題報告

Question Link

AC code

#include<iostream>
#include<cstdio>
using namespace std;
#define N  505
#define M 2005
 
int pre[N],dis[N],a[M],b[M];
char op[M];
 
int find(int x)
{
    if(x==pre[x]) return x;
    int t=pre[x];
    pre[x]=find(pre[x]);
    dis[x]=(dis[x]+dis[t])%3;
    return pre[x];
}
 
void Union(int x,int y,int fx,int fy,int w)
{
    pre[fy]=fx;
    dis[fy]=(dis[x]-dis[y]+w+3)%3;//這公式，我只能說是別人推出來，我枚舉驗證了一邊
}
 
int main()
{
    int i,j,n,m;
    while(~scanf("%d%d",&n,&m)){
        for(i=1;i<=m;i++){
            scanf("%d%c%d",&a[i],&op[i],&b[i]);
            if(op[i]=='=') op[i]=0;
            if(op[i]=='>') op[i]=1;
            if(op[i]=='<') op[i]=2;
        }
        int judge=-1,round=0;
        bool only=true;
        for(i=0;i<n;i++){
            bool f=true;
            for(j=0;j<n;j++){
                pre[j]=j;
                dis[j]=0;
            }
            for(j=1;j<=m;j++){
                if(a[j]==i||b[j]==i) continue;
                int fx=find(a[j]),fy=find(b[j]);
                if(fx==fy){
                    if(dis[b[j]]!=(dis[a[j]]+op[j])%3){
                        f=false;
                        round=max(round,j);
                        break;
                    }
                }
                else{
                    Union(a[j],b[j],fx,fy,op[j]);
                }
            }
            if(f){
                if(judge==-1)
                   judge=i;
                else{
                    only=false;
                    break;
                }
            }
        }
        if(judge==-1) puts("Impossible");
        else{
            if(!only) puts("Can not determine");
            else printf("Player %d can be determined to be the judge after %d lines\n",judge,round);
        }
    }
    return 0;
}