grasshop.cpp

#include <iostream>
#include <vector>
#include <queue>
 
using namespace std;
 
int dir[8][2] = {{1, 2}, {2, 1}, {2, -1}, {1, -2}, {-1, -2}, {-2, -1}, {-2, 1}, {-1, 2}};
 
struct point{
	point(int x_, int y_){x = x_; y = y_;}
	int x, y;
};
 
int main(){
	int R, C, Sy, Sx, Cy, Cx;
	while(cin >> R >> C >> Sy >> Sx >> Cy >> Cx){
		if(Sy == Cy && Sx == Cx){
			cout << 0 << '\n';
			continue;
		}
		vector<vector<int> > pole(R+1, vector<int> (C+1));
		queue<point> Q;
		Q.push(point(Sx, Sy));
		while(!Q.empty()){
			point p = Q.front();
			Q.pop();
			for(int i=0; i<8; ++i){
				int x = p.x + dir[i][0];
				int y = p.y + dir[i][1];
				if(x > 0 && x <= C && y > 0 && y <= R){
					if(pole[x][y] == 0){ 
						Q.push(point(x, y));
						pole[x][y] = pole[p.x][p.y] + 1;
						if(x == Cx && y == Cy){
							cout << pole[x][y] << '\n';
							goto LOOP;
						}
					}
				}
			}
		}
		cout << "impossible\n";
LOOP:;
 
	}
	return 0;
}