poj3278

BFS，注意判断数组是否越界，注意处理n==k的情况

View Code

   
     

    
      #include 
    
      <
    
      iostream
    
      >
    
      
#include 
    
      <
    
      cstdlib
    
      >
    
      
#include 
    
      <
    
      cstring
    
      >
    
      
#include 
    
      <
    
      cstdio
    
      >
    
      
#include 
    
      <
    
      queue
    
      >
    
      

    
      using
    
       
    
      namespace
    
       std;


    
      #define
    
       maxn 100005
    
      


    
      struct
    
       Item
{
 
    
      int
    
       step, pos;
 Item()
 {
 }
 Item(
    
      int
    
       s, 
    
      int
    
       p) :
 step(s), pos(p)
 {
 }
};


    
      int
    
       visited[maxn];


    
      int
    
       main()
{
 
    
      int
    
       n, k;
 
    
      //
    
      freopen("D:\\t.txt", "r", stdin);
    
      

    
       scanf(
    
      "
    
      %d%d
    
      "
    
      , 
    
      &
    
      n, 
    
      &
    
      k);
 
    
      if
    
       (n 
    
      ==
    
       k)
 {
 printf(
    
      "
    
      0\n
    
      "
    
      );
 
    
      return
    
       
    
      0
    
      ;
 }
 memset(visited, 
    
      0
    
      , 
    
      sizeof
    
      (visited));
 queue
    
      <
    
      Item
    
      >
    
       q;
 q.push(Item(
    
      0
    
      , n));
 
    
      while
    
       (
    
      1
    
      )
 {
 Item temp;
 temp 
    
      =
    
       q.front();
 q.pop();
 
    
      if
    
       (temp.pos 
    
      *
    
       
    
      2
    
       
    
      <
    
       maxn 
    
      &&
    
       
    
      !
    
      visited[temp.pos 
    
      *
    
       
    
      2
    
      ])
 {
 q.push(Item(temp.step 
    
      +
    
       
    
      1
    
      , temp.pos 
    
      *
    
       
    
      2
    
      ));
 visited[temp.pos 
    
      *
    
       
    
      2
    
      ] 
    
      =
    
       
    
      true
    
      ;
 }
 
    
      if
    
       (temp.pos 
    
      +
    
       
    
      1
    
       
    
      <
    
       maxn 
    
      &&
    
       
    
      !
    
      visited[temp.pos 
    
      +
    
       
    
      1
    
      ])
 {
 q.push(Item(temp.step 
    
      +
    
       
    
      1
    
      , temp.pos 
    
      +
    
       
    
      1
    
      ));
 visited[temp.pos 
    
      +
    
       
    
      1
    
      ] 
    
      =
    
       
    
      true
    
      ;
 }
 
    
      if
    
       (temp.pos 
    
      -
    
       
    
      1
    
       
    
      >=
    
       
    
      0
    
       
    
      &&
    
       
    
      !
    
      visited[temp.pos 
    
      -
    
       
    
      1
    
      ])
 {
 q.push(Item(temp.step 
    
      +
    
       
    
      1
    
      , temp.pos 
    
      -
    
       
    
      1
    
      ));
 visited[temp.pos 
    
      -
    
       
    
      1
    
      ] 
    
      =
    
       
    
      true
    
      ;
 }
 
    
      if
    
       (visited[k])
 {
 printf(
    
      "
    
      %d\n
    
      "
    
      , temp.step 
    
      +
    
       
    
      1
    
      );
 
    
      return
    
       
    
      0
    
      ;
 }
 }
 
    
      return
    
       
    
      0
    
      ;
}