BZOJ4602 [Sdoi2016]齿轮

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DFS，记录每个点转速，判断是否矛盾即可

#include<iostream>#include<cstdlib>#include<cstdio>#include<cstring>#include<cmath>#include<ctime>#include<algorithm>#include<iomanip>#include<vector>#include<stack>#include<queue>#include<map>#include<set>#include<bitset>using namespace std;#define MAXN 1010#define MAXM 10010#define ll long long#define INF 1000000000#define MOD 1000000007#define eps 1e-8struct vec{int to;int fro;double v;};vec mp[MAXM*2];int tai[MAXN],cnt;int n,m;double s[MAXN];bool vis[MAXN];inline void be(int x,int y,double z){mp[++cnt].to=y;mp[cnt].fro=tai[x];tai[x]=cnt;mp[cnt].v=z;}bool dfs(int x,double sp){int i,y;s[x]=sp;vis[x]=1;for(i=tai[x];i;i=mp[i].fro){y=mp[i].to;if(!vis[y]){if(dfs(y,sp*mp[i].v)){return 1;}}else{if(fabs(s[y]-sp*mp[i].v)>eps){return 1;}}}return 0;}int main(){int i,x,y,xx,yy;int tmp;scanf("%d",&tmp);int tcn=0;while(tmp--){tcn++;memset(tai,0,sizeof(tai));cnt=0;scanf("%d%d",&n,&m);for(i=1;i<=m;i++){scanf("%d%d%d%d",&x,&y,&xx,&yy);be(x,y,1.0*yy/xx);be(y,x,1.0*xx/yy);}memset(vis,0,sizeof(vis));bool flag=0;for(i=1;i<=n;i++){if(!vis[i]){if(dfs(i,1)){flag=1;break;}}}printf("Case #%d: ",tcn);printf(flag?"No\n":"Yes\n");}return 0;}/*23 31 2 3 52 3 5 -71 3 3 -73 31 2 3 52 3 5 -71 3 3 7*/

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