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,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
",spfa( n ) );
121     }
122     return 0;
123 }
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