最短路 spfa， dijkstra， Floyd

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spfa

 1 #include <stdio.h> 2 #include <queue> 3 using namespace std; 4  5 #define RANGE 101 6 #define MAX 0x3f3f3f3f 7 int cost[RANGE][RANGE]; 8 int d[RANGE]; 9 bool used[RANGE];10 int n,m;11 12 void spfa( int s )13 {14   int i,now;15   // 初始化16   for( i=1;i<=n;++i )17   {18     d[i]=MAX;19     used[i]=false;20   }21 22   d[s]=0;23   queue <int> q;24   q.push(s);25   used[s] = true;26 27   while(!q.empty())28   {29     now = q.front();30     q.pop();31     used[now] = false;32     for(i = 1; i <= n; i++)33     {34       if(d[i] > d[now] + cost[now][i])35       {36         d[i] = d[now] + cost[now][i];37         if(used[i] == 0)38         {39           q.push(i);40           used[i] = true;41         }42       }43     }44   }45 }46 47 int main()48 {49   int i,j,A,B,C;50   while( scanf("%d%d",&n,&m) )51   {52     if( !n && !m )  break;53     // 初始化54     for( i=1;i<=n;++i )55       for( j=1;j<=i;++j )56         if( i==j )  cost[i][j]=0;57         else    cost[i][j]=cost[j][i]=MAX;58 59     for( i=0;i<m;++i )60     {61       scanf("%d%d%d",&A,&B,&C);62       cost[A][B]=cost[B][A]=C;63     }64 65     spfa(1);66     printf("%d\n",d[n]);67   }68   return 0;69 }

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dijkstra

 1 #include <stdio.h> 2 #define MAX 0x3f3f3f3f 3 #define RANGE 101 4  5 int cost[RANGE][RANGE]; 6 int d[RANGE]; 7 bool used[RANGE]; 8  9 int n,m;10 int Min( int a,int b )11 {12   return a<b?a:b;13 }14 15 void Dijkstra( int s )16 {17   int i,v,u;18   for( i=1;i<=n;++i )19   {20     used[i]=false;21     d[i]=cost[1][i];22   }23   d[s]=0;24 25   while( true )26   {27     v=-1;28     for( u=1;u<=n;++u )29       if( !used[u] && ( v==-1 || d[u]<d[v]) )30         v=u;31     if( v==-1 ) break;32     used[v]=true;33 34     for( u=1;u<=n;++u )35       d[u]=Min( d[u],d[v]+cost[v][u] );36   }37 }38 39 int main()40 {41   int A,B,C,i,j;42 43   while( scanf("%d%d",&n,&m) )44   {45     if( !n && !m )  break;46 47     // 初始化48     for( i=1;i<=n;++i )49       for( j=1;j<=i;++j )50         if( i==j )  cost[i][j]=0;51         else    cost[i][j]=cost[j][i]=MAX;52 53     for( i=0;i<m;++i )54     {55       scanf("%d%d%d",&A,&B,&C);56       cost[A][B]=cost[B][A]=C;57     }58 59     Dijkstra(1);60     printf("%d\n",d[n]);61   }62   return 0;63 }

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floyd

 1 #include <stdio.h> 2 #define MAX 0x3f3f3f3f 3 #define RANGE 105 4  5 int d[RANGE][RANGE]; 6 int n; 7  8 int Min( int a,int b ) 9 {10   return a<b?a:b;11 }12 void warshall_floyd( void )13 {14   int i,j,k;15   for( k=1;k<=n;++k )16     for( i=1;i<=n;++i )17       for( j=1;j<=n;++j )18         d[i][j]=Min( d[i][j],d[i][k]+d[k][j] );19 }20 21 int main()22 {23   int m,A,B,C,i,j;24 25   while( scanf("%d%d",&n,&m) )26   {27     if( !n && !m )  break;28 29     // 初始化30     for( i=1;i<=n;++i )31       for( j=1;j<=i;++j )32       {33         if( i==j ) d[i][j]=0;34         else    d[i][j]=d[j][i]=MAX;35       }36 37     // 输入38     for( i=0;i<m;++i )39     {40       scanf("%d%d%d",&A,&B,&C);41       d[A][B]=d[B][A]=C;42     }43 44     // floyd算法求最短路45     warshall_floyd();46     printf("%d\n",d[1][n]);47   }48   return 0;49 }

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