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| #include<bits/stdc++.h>
struct Case{
int x, y, t;
};
Case C[10005];
int m[105][105], c[105][105];
int main(){
int n, x, y, bx, by, top=0, bot=0 ,a ,b;
scanf("%d", &n);
for(int i=0; i<n; i++){
scanf("%d%d", &a, &b);
m[a+3][b+3] = 1;
}
scanf("%d%d", &x, &y);
scanf("%d%d", &bx, &by);
bx+=3;
by+=3;
C[top].x = x+3;
C[top].y = y+3;
C[top].t = 0;
bot++;
memset(c, 0, sizeof(c));
while((C[top].x!=bx||C[top].y!=by)&&top!=bot){
if(!(C[top].x<3||C[top].x>102||C[top].y<3||C[top].y>102)){
if(!m[C[top].x+1][C[top].y]){
if(!c[C[top].x+3][C[top].y+1]&&!m[C[top].x+3][C[top].y+1]){
c[C[top].x+3][C[top].y+1]++;
C[bot].x = C[top].x+3;
C[bot].y = C[top].y+1;
C[bot].t = C[top].t+1;
bot++;
}
if(!c[C[top].x+3][C[top].y-1]&&!m[C[top].x+3][C[top].y-1]){
c[C[top].x+3][C[top].y-1]++;
C[bot].x = C[top].x+3;
C[bot].y = C[top].y-1;
C[bot].t = C[top].t+1;
bot++;
}
}
if(!m[C[top].x-1][C[top].y]){
if(!c[C[top].x-3][C[top].y+1]&&!m[C[top].x-3][C[top].y+1]){
c[C[top].x-3][C[top].y+1]++;
C[bot].x = C[top].x-3;
C[bot].y = C[top].y+1;
C[bot].t = C[top].t+1;
bot++;
}
if(!c[C[top].x-3][C[top].y-1]&&!m[C[top].x-3][C[top].y-1]){
c[C[top].x-3][C[top].y-1]++;
C[bot].x = C[top].x-3;
C[bot].y = C[top].y-1;
C[bot].t = C[top].t+1;
bot++;
}
}
if(!m[C[top].x][C[top].y+1]){
if(!c[C[top].x+1][C[top].y+3]&&!m[C[top].x+1][C[top].y+3]){
c[C[top].x+1][C[top].y+3]++;
C[bot].x = C[top].x+1;
C[bot].y = C[top].y+3;
C[bot].t = C[top].t+1;
bot++;
}
if(!c[C[top].x-1][C[top].y+3]&&!m[C[top].x-1][C[top].y+3]){
c[C[top].x-1][C[top].y+3]++;
C[bot].x = C[top].x-1;
C[bot].y = C[top].y+3;
C[bot].t = C[top].t+1;
bot++;
}
}
if(!m[C[top].x][C[top].y-1]){
if(!c[C[top].x+1][C[top].y-3]&&!m[C[top].x+1][C[top].y-3]){
c[C[top].x+1][C[top].y-3]++;
C[bot].x = C[top].x+1;
C[bot].y = C[top].y-3;
C[bot].t = C[top].t+1;
bot++;
}
if(!c[C[top].x-1][C[top].y-3]&&!m[C[top].x-1][C[top].y-3]){
c[C[top].x-1][C[top].y-3]++;
C[bot].x = C[top].x-1;
C[bot].y = C[top].y-3;
C[bot].t = C[top].t+1;
bot++;
}
}
}
top++;
}
if(C[top].t==0) printf("impossible\n");
else printf("%d\n", C[top].t);
}
|