CSU1321+SPFA

简单题

  1 /*

  2 简单的bfs

  3 */

  4 #include<algorithm>

  5 #include<iostream>

  6 #include<string.h>

  7 #include<stdlib.h>

  8 #include<stdio.h>

  9 #include<math.h>

 10 #include<queue>

 11 #include<stack>

 12 #include<map>

 13 #include<set>

 14 using namespace std;

 15 typedef long long int64;

 16 //typedef __int64 int64;

 17 typedef pair<int64,int64> PII;

 18 #define MP(a,b) make_pair((a),(b)) 

 19 const int inf = 0x3f3f3f3f;

 20 const double pi=acos(-1.0);

 21 const int dx[]={1,-1,0,0};

 22 const int dy[]={0,0,1,-1};

 23 const double eps = 1e-8;

 24 const int maxm = 1000005;

 25 const int maxn = 1005;

 26 struct Edge{

 27     int u,v,next,val;

 28 }edge[ maxm*2 ];

 29 int cnt ,head[ maxn ];

 30 bool vis[ maxn ];

 31 int dis1[ maxn ],dis2[ maxn ],girl[ maxn ];

 32 //int dp[ maxn ];

 33 queue<int>q;

 34 //int pre[ maxn ];

 35 void init(){

 36     cnt = 0;

 37     memset( head,-1,sizeof( head ) );

 38 }

 39 void addedge( int a,int b,int c ){

 40     edge[ cnt ].u = a;

 41     edge[ cnt ].v = b;

 42     edge[ cnt ].val = c;

 43     edge[ cnt ].next = head[ a ];

 44     head[ a ] = cnt ++;

 45 }

 46 

 47 int spfa( int n ){

 48     while( !q.empty() )

 49         q.pop();

 50     //memset( pre,-1,sizeof( pre ) );

 51     memset( vis,false,sizeof( vis ) );

 52     memset( dis1,0x3f,sizeof( dis1 ) );

 53     memset( dis2,0x3f,sizeof( dis2 ) );

 54     vis[ 1 ] = true;

 55     q.push( 1 );

 56     dis1[ 1 ] = 0;

 57     dis2[ 1 ] = girl[ 1 ];

 58     //for( int i=head[1];i!=-1;i=edge[i].next ){

 59     //    pre[ edge[i].v ] = 1;

 60     //}

 61     while( !q.empty() ){

 62         int cur = q.front();

 63         q.pop();

 64         vis[ cur ] = false;

 65         for( int i=head[cur];i!=-1;i=edge[i].next ){

 66             int nxt = edge[ i ].v;

 67             if( dis1[nxt]>dis1[cur]+edge[i].val ){

 68                 dis1[nxt] = dis1[cur]+edge[i].val;

 69                 //pre[ nxt ] = cur;

 70                 dis2[nxt] = dis2[cur]+girl[edge[i].v];

 71                 if( !vis[nxt] ){

 72                     vis[nxt] = true;

 73                     q.push( nxt );

 74                 }

 75             }

 76             else if( dis1[nxt]==dis1[cur]+edge[i].val ){

 77                 if( dis2[nxt]<dis2[cur]+girl[edge[i].v] ){

 78                     //pre[ nxt ] = cur;

 79                     dis2[nxt]=dis2[cur]+girl[edge[i].v];

 80                     if( !vis[nxt] ){

 81                         vis[nxt] = true;

 82                         q.push( nxt );

 83                     }

 84                 }

 85             }

 86         }

 87     }

 88     //printf("dis1[ %d ] = %d\n",n,dis1[n]);

 89     if( dis1[n]>=0x3f3f3f3f ) return -1;

 90     else return dis2[ n ];

 91     /*

 92     int ans = 0;

 93     int cur = n;

 94     while( 1 ){

 95         ans += girl[ cur ];

 96         cur = pre[ cur ];

 97         if( cur==-1 ){

 98             break;

 99         }

100     }

101     return ans;

102     */

103 }

104     

105 int main(){

106     int n;

107     while( scanf("%d",&n)==1 ){

108         int m;

109         scanf("%d",&m);

110         for( int i=1;i<=n;i++ )

111             scanf("%d",&girl[i]);

112         int a,b,c;

113         init();

114         while( m-- ){

115             scanf("%d%d%d",&a,&b,&c);

116             //if( a==b ) continue;

117             addedge( a,b,c );

118             addedge( b,a,c );

119         }

120         printf("%d\n",spfa( n ) );

121     }

122     return 0;

123 }

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