POJ - 3126 Prime Path

  1 #include<stdio.h>
  2 #include<assert.h>
  3 #include<cmath>
  4 #include<string.h>
  5 //#include<queue>
  6 const int maxn=15000+5;
  7 int s[10];
  8 int vis[maxn],isp[maxn];
  9 using namespace std;
 10 struct node{
 11     int num;
 12     int cost;
 13     void init(int x,int y){
 14         num=x;
 15         cost=y;
 16     }
 17 }queue[maxn];
 18 int is_prime(int x)
 19 {
 20     int k=sqrt(x);
 21     k=floor(k)+1;
 22     assert(x>0);
 23     if(x<=2)
 24         return 1;
 25     for(int i=2;i<=k;i++)
 26         if(x%i==0)
 27         return 0;
 28     return 1;
 29 }
 30 int bfs(node source,node target)
 31 {
 32     int tail,head;
 33     source.cost=0;
 34     queue[tail=head=0].num=source.num;
 35     queue[tail++].cost=0;
 36 //    queue<node>q;
 37 //    q.push(source);
 38     memset(vis,0,sizeof(vis));
 39     vis[source.num]=1;
 40     if(source.num==target.num)
 41         return 0;
 42     while(head<tail){
 43 //        node a=q.front();
 44 //        q.pop();
 45         node a=queue[head];
 46         int temp,midvar=a.num,cot=3;
 47         while(midvar){
 48             s[cot--]=midvar%10;
 49             midvar/=10;
 50         }
 51 //        sprintf(s,"%d",a.num);
 52 //        int len=strlen(s);
 53         for(int i=0;i<4;i++){
 54             int bufvar=s[i];
 55             for(int j=0;j<10;j++){
 56                 if(i==0 && j!=0 && s[i]!=j){
 57                     s[i]=j;
 58                     temp=s[0]*1000+s[1]*100+s[2]*10+s[3];
 59 //                    sscanf(s,"%d",&temp);
 60 //                    printf("%d\n",temp);
 61                     if(temp==target.num)
 62                         return a.cost+1;
 63                     if(isp[temp] && !vis[temp]){
 64 //                        c.init(temp, a.cost+1);
 65 //                        q.push(c);
 66                         queue[tail].num=temp;
 67                         queue[tail].cost=queue[head].cost+1;
 68                         tail++;
 69                         vis[temp]=1;
 70                     }
 71                 }
 72                 if(i!=0 && s[i]!=j){
 73                     s[i]=j;
 74                     temp=s[0]*1000+s[1]*100+s[2]*10+s[3];
 75 //                    sscanf(s,"%d",&temp);
 76                     if(temp==target.num)
 77                         return a.cost+1;
 78                     if(isp[temp] && !vis[temp]){
 79                         queue[tail].num=temp;
 80                         queue[tail].cost=queue[head].cost+1;
 81                         tail++;
 82                         vis[temp]=1;
 83                     }
 84                 }
 85             }
 86             s[i]=bufvar;
 87         }
 88         head++;
 89     }
 90     return -1;
 91 }
 92 int main()
 93 {
 94     int t;
 95     scanf("%d",&t);
 96     while(t--){
 97         node source,target;
 98         scanf("%d%d",&source.num,&target.num);
 99         memset(isp,0,sizeof(isp));
100         for(int i=1001;i<10000;i++)
101             if(is_prime(i))
102             isp[i]=1;
103         int mincost=bfs(source,target);
104         printf("%d\n",mincost);
105     }
106     return 0;