grasshop.cpp

#include <iostream>
#include <algorithm>
#include <cstdlib>
#include <queue>
#include <climits>
#include <cstdio>		
 
 
using namespace std;
 
int field[105][105];
bool vis[105][105];
int x[] = {1,2,2,1,-1,-2,-2,-1};
int y[] = {-2,-1,1,2,2,1,-1,-2};
 
int r,c,gx,gy,lx,ly;
 
bool check(int x, int y){
	if(x < 1 || x >= c || y < 1 || y >= r)
		return false;
	return true;
}
 
int main(){
 
	while(cin >> r >> c>>gy>>gx>>ly>>lx){
		for(int i = 0; i < r + 1; i++)
			for(int j = 0; j < c + 1; j++)
				vis[i][j] = false;
 
		queue < pair <int,int> > q;
		q.push( pair<int,int>(gx,gy) );
		field[gy][gx] = 0;
		vis[gy][gx] = true;
		bool ok = false;
 
		pair<int,int> fq;
		while(!q.empty()){
			fq = q.front();
			q.pop();
 
			if(fq.first == lx && fq.second == ly){
				ok = true;
				break;
			}
 
			for(int i = 0; i < 8; i++){
				if(check(fq.first + x[i], fq.second + y[i]))
					if(!vis[fq.second + y[i]][fq.first + x[i]]){
						vis[fq.second + y[i]][fq.first + x[i]] = true;
						field[fq.second + y[i]][fq.first + x[i]] = field[fq.second][fq.first] + 1;
						q.push( pair<int,int>(fq.first + x[i],fq.second + y[i]) );
					}
			}
		}
		if(ok)
			cout << field[ly][lx] << endl;
		else
			cout << "impossible" << endl;
 
	}
 
 
 
return 0;
}