打水题啊打水题。。。然后就被虐了。。。
看不懂题目，后来查hzwer的blog，发现时题目翻译错了。。。我去我就说我的语文怎么这么差。
hzwer："总之就是在地图上从2出发，走到3，途中要至少经过一个4。"
原来如此，不就是两次bfs嘛。。。只是第一次bfs的时候要注意不能经过4。
然后开始bfs，在快要写死的时候。。。终于对了。。。
哈哈，status第六哦~~~不错不错
1 /************************************************************** 2 Problem: 1671 3 User: rausen 4 Language: C++ 5 Result: Accepted 6 Time:168 ms 7 Memory:16548 kb 8 ****************************************************************/ 9 10 #include <cstdio> 11 #include <algorithm> 12 13 using namespace std; 14 const int inf = (int) 1e9; 15 const int dx[4] = {0, 0, -1, 1}; 16 const int dy[4] = {1, -1, 0, 0}; 17 18 struct QUEUE{ 19 int x, y; 20 }q[500005]; 21 int d[2][1005][1005], mp[1005][1005]; 22 int n, m, sx[2], sy[2]; 23 24 inline int read(){ 25 int x = 0, sgn = 1; 26 char ch = getchar(); 27 while (ch < '0' || ch > '9'){ 28 if (ch == '-') sgn = -1; 29 ch = getchar(); 30 } 31 while (ch >= '0' && ch <= '9'){ 32 x = x * 10 + ch - '0'; 33 ch = getchar(); 34 } 35 return sgn * x; 36 } 37 38 inline bool check(int x, int y){ 39 return x < 1 || y < 1 || x > n || y > m; 40 } 41 42 void bfs(int p){ 43 q[0].x = sx[p], q[0].y = sy[p], d[p][sx[p]][sy[p]] = 0; 44 int x, y, X, Y; 45 for (int l = 0, r = 0; l <= r; ++l){ 46 X = q[l].x, Y = q[l].y; 47 for (int i = 0; i < 4; ++i){ 48 x = X + dx[i], y = Y + dy[i]; 49 if (check(x, y) || mp[x][y] == 1 || d[p][x][y] != -1) continue; 50 ++r; 51 q[r].x = x, q[r].y = y; 52 d[p][x][y] = d[p][X][Y] + 1; 53 } 54 } 55 } 56 57 int getans(){ 58 int res = inf; 59 for (int i = 1; i <= n; ++i) 60 for (int j = 1; j <= m; ++ j){ 61 if (d[0][i][j] == -1 || d[1][i][j] == -1 || mp[i][j] != 4) continue; 62 res = min(res, d[0][i][j] + d[1][i][j]); 63 } 64 return res; 65 } 66 67 int main(){ 68 m = read(), n = read(); 69 for (int i = 1; i <= n; ++i) 70 for (int j = 1; j <= m; ++j){ 71 d[0][i][j] = d[1][i][j] = -1; 72 mp[i][j] = read(); 73 if (mp[i][j] == 2) 74 sx[0] = i, sy[0] = j; 75 if (mp[i][j] == 3) 76 sx[1] = i, sy[1] = j; 77 } 78 79 bfs(0); bfs(1); 80 printf("%d ", getans()); 81 return 0; 82 }