[BFS] horse traversal

 Subject to the effect

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Title Description 

N * m has a board ( . 1 <n-, m <= 400 ), there is a horse at some point, requires you to go happened in arbitrary point on the board reaches a short run for

 Input Format

A row of four coordinate data, the size of the board and horse

Output Format

A matrix of n * m, horse reaches a point representative of a minimum of steps to go (left, 5 wide grid does not reach the Output - . 1 )

Sample input and output

Input # 1

3 3 1 1

Output # 1

0    3    2    
3    -1   1    
2    1    4    

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Thinking

Wide search + STL queue 
using the structure variable Pos stored coordinates 
using two-dimensional array of the Map [ 401 ] [ 401 ] memory map (answer) 
using constant array dx [] dy [] storage horses can go eight directions 
using the type of queue Pos maintenance value of the coordinate point

 

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Code

 

#include <Queue> 
#include <CString> 
#include <cstdio>
 the using  namespace STD;
 struct Pos // structure variables Pos, horse store x, y coordinate values 
{
     int x, y; 
}; 
Queue <Pos> Q; // definition of a type Pos queue Q 
int n-, m, TX, TY, MP [ 401 ] [ 401 ], X, Y;
 const  int DX [] {= - . 1 , - . 1 , - 2 , - 2 , . 1 , . 1 , 2 , 2 };
 const  int Dy [] = {-2 , 2 - 1 , 1 - 2 , 2 - 1 , 1 }; // 8 directions horse 
void BFS ( int SX, int SY) 
{ 
    q.push ((Pos) {SX, SY}) ; // insertion process values 
    MP [SX] [SY] = 0 ;
     the while (! q.empty ()) 
    { 
        X = q.front () X;. 
        Y = q.front () Y;. 
        q.pop (); 
        for ( int I = 0 ; I < . 8;i++)
        {
            tx=x+dx[i];
            ty=y+dy[i];
            if(tx<=0||tx>n||ty<=0||ty>m) continue;
            if(mp[tx][ty]!=-1) continue;
            mp[tx][ty]=mp[x][y]+1;
            q.push((Pos){tx,ty});
        }
    }
}
int main()
{
    memset(mp,-1,sizeof(mp));
    int sx,sy;
    scanf("%d %d %d %d",&n,&m,&sx,&sy);
    bfs(sx,sy);
    for(int i=1;i<=n;i++)
    {
        for(int j=1;j<=m;j++)
            printf("%-5d",mp[i][j]); //注意输出格式
        printf("\n");
    }
    return 0;
}

 

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