2017.11.8. Floyed求最小环

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Floyed求最小环

适合题型：

1.求最小环

样题： HDU1599

std.cpp：

#include<iostream>#include<iomanip>#include<cstdio>#include<cstdlib>#include<string>#include<cstring>#include<algorithm>#include<cmath>#include<queue>#include<vector>using namespace std;inline int read(){    int x=0,w=1;char ch=0;    while(ch< '0'||'9' <ch){if(ch=='-')w=-1;ch=getchar();}    while(ch>='0'&&ch<='9'){x=(x<<3)+(x<<1)+ch-'0';ch=getchar();}    return x*w;}typedef long long ll;inline ll red(){    ll x=0,w=1;char ch=0;    while(ch< '0'||'9' <ch){if(ch=='-')w=-1;ch=getchar();}    while(ch>='0'&&ch<='9'){x=(x<<3)+(x<<1)+ch-'0';ch=getchar();}    return x*w;}#define maxx 2000inline char *get_str(char *str){    fgets(str,maxx,stdin);    if(str[strlen(str)-1]=='\n')        str[strlen(str)-1]='\0';    return str;}int n,m,u,v,val;int f[105][105],dis[105][105];int main(){    while(~scanf("%d%d",&n,&m))    {        for(int i=1;i<=n;i++)               for(int j=1;j<=n;j++)                f[i][j]=1e8,dis[i][j]=1e8;        for(int i=1;i<=m;i++)        {            u=read();v=read();val=read();            f[u][v]=f[v][u]=dis[u][v]=dis[v][u]=min(val,f[u][v]);        }        int ans=1e8;        for(int k=1;k<=n;k++)        {            for(int i=1;i<k;i++)                for(int j=i+1;j<k;j++)                    ans=min(ans,dis[i][j]+f[i][k]+f[k][j]);            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]);           }        if(ans==1e8)cout<<"It's impossible."<<endl;        else    cout<<ans<<endl;    }    return 0;}

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