grasshop.cpp

#include <queue>
#include <cstdio>
#include <utility>
using namespace std;
 
int  jumps[8][2] = {{1,2},{2,1},{-1,2},{-2,1},{1,-2},{2,-1},{-1,-2},{-2,-1}};
int main(void){
  int r,c,gr,gc,lr,lc;
  int pole[100][100];
  while (scanf("%d %d %d %d %d %d",&r,&c,&gr,&gc,&lr,&lc)==6){
    queue<pair<int,int> > Q;
    gr--;
    gc--;
    lc--;
    lr--;
    Q.push(pair<int,int>(gr,gc));
    for (int i = 0; i<r; i++){
      for (int j = 0; j<c; j++){
	pole[i][j]=100000;
      }
    } 
 
    pole[gr][gc]=0;
    while(!Q.empty()){
      pair<int,int> p = Q.front();
      Q.pop();
      for (int i=0; i<9; i++){
	int x =p.first+jumps[i][0];
	int y =p.second+jumps[i][1];
	if ((x>=0 && y >=0 && x <r && y <c)&& (pole[x][y]>pole[p.first][p.second]+1)){
	  Q.push(pair<int,int>(x,y));
	  pole[x][y]=pole[p.first][p.second]+1;
	  if (x == lr && y == lc)
	    goto konec;
	  }
      }
 
    }
  konec:
    if (pole[lr][lc]== 100000)
      printf("impossible\n");
    else
      printf("%d\n", pole[lr][lc]);
  }
 
}