hdu 3085 双向BFS

#include <iostream>
#include <cstdio>
#include <cstring>
#include <string>
#include <queue>
#include <cmath>
using namespace std;

int N, M;
bool visit[2][801][801];
int maps[801][801];
int gx, gy, mx, my;
int z[2][2];
int step;
int moves[4][2] = { 1, 0, -1, 0, 0, 1, 0, -1 };
queue< pair<int,int> > q[2];

bool judge( int x, int y ){
if( x >= 0 && x < N && y >= 0 && y < M && maps[x][y] != 0 ){
for( int i = 0; i < 2; i++ ){
if( abs( ( x - z[i][0] ) ) + abs( y - z[i][1] ) <= 2 * step ){//这里不要把x-z[i][0]变成double 不然会超时
return false;
}
}
return true;
}
return false;
}

bool BFS( int num ){
int size = q[num].size();

while( size-- ){
int x = q[num].front().first;
int y = q[num].front().second;
q[num].pop();
if( !judge( x, y ) ){
continue;
}
for( int i = 0; i < 4; i++ ){
int xx = x + moves[i][0];
int yy = y +  moves[i][1];
if( judge( xx, yy ) ){
if( visit[num][xx][yy] ){
continue;
}
if( visit[num^1][xx][yy] ){
return true;
}
visit[num][xx][yy] = true;
q[num].push( make_pair( xx, yy ) );
}
}
}
return false;
}

int solve(){
while( !q[0].empty() ){
q[0].pop();
}
while( !q[1].empty() ){
q[1].pop();
}
q[0].push( make_pair( mx, my ) );
q[1].push( make_pair( gx, gy ) );
visit[0][mx][my] = visit[1][gx][gy] = true;
step = 0;

while( !q[0].empty() || !q[1].empty() ){
step++;
if( BFS( 0 ) ) return step;
if( BFS( 0 ) ) return step;
if( BFS( 0 ) ) return step;
if( BFS( 1 ) ) return step;
}
return -1;
}

int main(){
int Case;
string s;

cin >> Case;
while( Case-- ){
cin >> N >> M;
int temp = 0;
for( int i = 0; i < N; i++ ){
cin >> s;
for( int j = 0; j < M; j++ ){
if( s[j] == 'X' ){
maps[i][j] = 0;
}else if( s[j] == 'Z' ){
maps[i][j] = 0;
z[temp][0] = i;
z[temp++][1] = j;
}else if( s[j] == '.' ){
maps[i][j] = 1;
}else if( s[j] == 'M' ){
mx = i;
my = j;
maps[i][j] = 1;
}else{
gx = i;
gy = j;
maps[i][j] = 1;
}
}
}
memset( visit, false, sizeof( visit ) );

cout << solve() << endl;
}
return 0;
}