grasshop.cpp
#include <cstdio>
#include <cstring>
using namespace std;
void enqueue(int x, int y, int distance, int queueX[10000], int queueY[10000], int &queueLen, int dist[100][100], int rows, int cols) {
if(dist[x][y] != 0) return;
if(x < 0 || x >= cols) return;
if(y < 0 || y >= rows) return;
queueX[queueLen] = x;
queueY[queueLen] = y;
dist[x][y] = distance + 1;
++queueLen;
}
int main(void) {
while(true) {
int rows, cols, sx, sy, tx, ty;
if(scanf("%d%d%d%d%d%d\n", &rows, &cols, &sx, &sy, &tx, &ty) != 6) {
break;
}
--sx;
--sy;
--tx;
--ty;
int dist[100][100];
for(int i = 0; i < cols; ++i) {
for(int j = 0; j < rows; ++j) {
dist[i][j] = 0;
}
}
int queueX[10000], queueY[10000];
int queueLen = 1;
int queuePos = 0;
queueX[0] = sx;
queueY[0] = sy;
dist[sx][sy] = 1;
int curX, curY, curDist;
while(queuePos < queueLen) {
curX = queueX[queuePos];
curY = queueY[queuePos];
curDist = dist[curX][curY];
if(curX == tx && curY == ty) break;
enqueue(curX + 2, curY + 1, curDist, queueX, queueY, queueLen, dist, rows, cols);
enqueue(curX + 2, curY - 1, curDist, queueX, queueY, queueLen, dist, rows, cols);
enqueue(curX + 1, curY + 2, curDist, queueX, queueY, queueLen, dist, rows, cols);
enqueue(curX + 1, curY - 2, curDist, queueX, queueY, queueLen, dist, rows, cols);
enqueue(curX - 1, curY + 2, curDist, queueX, queueY, queueLen, dist, rows, cols);
enqueue(curX - 1, curY - 2, curDist, queueX, queueY, queueLen, dist, rows, cols);
enqueue(curX - 2, curY + 1, curDist, queueX, queueY, queueLen, dist, rows, cols);
enqueue(curX - 2, curY - 1, curDist, queueX, queueY, queueLen, dist, rows, cols);
++queuePos;
}
int minDist = dist[tx][ty];
if(minDist == 0) {
printf("impossible\n");
}
else {
printf("%d\n", minDist - 1);
}
}
}