最优贸易

  1 #include <iostream>
  2 #include <fstream>
  3 #include <cstdlib>
  4 #include <cstring>
  5 using namespace std;
  6 /* run this program using the console pauser or add your own getch, system("pause") or input loop */
  7 ifstream fin("trade.in");
  8 ofstream fout("trade.out");
  9 
 10 int cnt_city=0,cnt_rode=0;
 11 int city_jia[100005]={0};
 12 int shun_tou[100005]={0},shun_cnt=0;
 13 int ni_tou[100005]={0},ni_cnt=0;
 14 struct tu{
 15  int nxt;
 16  int to;    
 17 };
 18  tu shunxu[500005]={0};
 19  tu nixu[500005]={0};
 20 int zx_jia[100005]={0};
 21 int zd_jia[100005]={0}; 
 22 int dui[1000005]={0}; 
 23 bool zai[500005]={0};
 24 
 25 void add(int a,int b );
 26 void zadd(int a,int b);
 27 void spfa_shun(      );
 28 void spfa_ni( );
 29 void output( );
 30 
 31 void add(int a,int b){
 32  shunxu[++shun_cnt].nxt=shun_tou[a];
 33  shunxu[shun_cnt].to=b;
 34  shun_tou[a]=shun_cnt;
 35  return;
 36 }
 37 
 38 
 39 void zadd(int a,int b){
 40  nixu[++ni_cnt].nxt=ni_tou[a];
 41  nixu[ni_cnt].to=b;
 42  ni_tou[a]=ni_cnt;
 43  return;         
 44 }
 45 
 46 
 47 void spfa_shun( ){
 48  int head=0,tail=1;    
 49  dui[1]=1,zx_jia[1]=city_jia[1],zd_jia[1]=city_jia[1];
 50  zai[1]=1;
 51  do{
 52   head++;
 53   if(head>1000003)head=1;
 54   int cong=dui[head];
 55   for(int hao=shun_tou[cong];hao!=-1;hao=shunxu[hao].nxt){
 56    int dao=shunxu[hao].to;
 57    int xiao=min(zx_jia[cong],city_jia[dao]);
 58    if(xiao<zx_jia[dao]){
 59        zx_jia[dao]=xiao;
 60        if(zai[dao]==0){
 61         tail++;
 62         if(tail>1000003)tail=1;
 63      dui[tail]=dao;    
 64      zai[dao]=1;       
 65     }
 66    }    
 67    
 68   }
 69   zai[cong]=0;
 70  }while(head!=tail);    
 71  return;    
 72 }
 73 
 74 
 75 void spfa_ni( ){
 76  memset(dui,0,sizeof(dui));
 77  memset(zai,0,sizeof(zai));
 78  int head=0,tail=1;    
 79  dui[1]=cnt_city;
 80  zai[cnt_city]=1;
 81  do{
 82   head++;
 83   if(head>1000003)head=1;
 84   int cong=dui[head];
 85   for(int hao=ni_tou[cong];hao!=-1;hao=nixu[hao].nxt){
 86    int dao=nixu[hao].to;
 87    int da=max(zd_jia[cong],city_jia[dao]);
 88    if(da>zd_jia[dao]){
 89        zd_jia[dao]=da;
 90         tail++;
 91         if(tail>1000003)tail=1;
 92      dui[tail]=dao;    
 93      zai[dao]=1;       
 94     
 95    } 
 96    if(zai[dao]==0){
 97        zai[dao]=1;
 98     tail++;
 99     if(tail>1000003)tail=1;
100     dui[tail]=dao;    
101    } 
102   }
103  }while(head!=tail);    
104  return;    
105 }
106 
107 
108 void output( ){
109  int max_mon=0;    
110  for(int x=1;x<=cnt_city;x++){
111   //cout<<zd_jia[x]<<" "<<zx_jia[x]<<endl;
112   if(zai[x]==1)    
113   max_mon=max(max_mon,zd_jia[x]-zx_jia[x]);    
114  }    
115  cout<<max_mon;    
116  fout<<max_mon;    
117 }
118 
119 
120 int main(int argc, char *argv[]){
121  fin>>cnt_city>>cnt_rode;
122  for(int x=1;x<=cnt_city;x++)fin>>city_jia[x];
123  memset(shun_tou,-1,sizeof(shun_tou));
124  memset(ni_tou,-1,sizeof(ni_tou));
125  for(int x=1;x<=cnt_rode;x++){
126   int a,b,c;
127   fin>>a>>b>>c;
128   add(a,b);
129   zadd(b,a);
130   if(c==2){
131    add(b,a);
132    zadd(a,b);
133   }
134  }
135 
136  memset(zx_jia,0x7f,sizeof(zx_jia));
137  memset(zd_jia,-1,sizeof(zd_jia));
138  spfa_shun( );  
139  spfa_ni( );
140  
141  output( );
142  
143  return 0;
144 }