程序代码：

#include <stdio.h> 
#include <stdlib.h> 
#include <string.h> 

#define max_m 1000 
#define max_n 1000 

int dir[4][2] = {{1,0},{-1,0},{0,1},{0,-1}}; 
int maze[max_m][max_n]; 
int m,n,start_row,start_col,end_row,end_col; 
char c; 

void read_maze() 
{ 
int i,j; 
char buf[256]; 
memset(buf, 0, sizeof(buf)); 
fgets(buf, 256, stdin); 
sscanf(buf, "%d%d", &m, &n); 
fgets(buf, 256, stdin); 
sscanf(buf, "%d%d", &start_row, &start_col); 
start_row--;start_col--; 
fgets(buf, 256, stdin); 
sscanf(buf, "%d%d", &end_row, &end_col); 
end_row--;end_col--; 
for (i = 0; i < m; i++) 
{ 
for (j = 0; j < n; j++) 
{ 
scanf("%c", &c); 
maze[i][j] = (c != '.'); 
} 
fgets(buf, 256, stdin); 
} 
} 

int new_value(int row, int col) 
{ 
int i,new_row,new_col; 
int result; 
result = maze[row][col]; 
if (result == 0) 
{ 
for (i = 0; i < 4; i++) 
{ 
new_row = row + dir[i][0]; 
new_col = col + dir[i][1]; 
if (new_row >= 0 && new_row < m && new_col >= 0 && new_col < n && maze[new_row][new_col] < 0 && (result == 0 || maze[new_row][new_col] - 1 > result)) 
{ 
result = maze[new_row][new_col] - 1; 
} 
} 
} 
return result; 
} 

int find_shortest_path() 
{ 
int changed,i,j,new_val,expect_val; 
if (start_row < 0 || start_row >= m || start_col < 0 || start_col >= n || end_row < 0 || end_row >= m || end_col < 0 || end_col >= n || maze[start_row][start_col] != 0 || maze[end_row][end_col] != 0) 
{ 
return 0; 
} 
changed = 1; 
maze[end_row][end_col] = -1; 
expect_val = -2; 
while (changed && maze[start_row][start_col] == 0) 
{ 
changed = 0; 
for (i = 0; i < m; i++) 
for (j = 0; j < n; j++) 
{ 
new_val = new_value(i,j); 
if (new_val == expect_val && new_val != maze[i][j]) 
{ 
maze[i][j] = new_val; 
changed = 1; 
} 
} 
expect_val--; 
} 
return (maze[start_row][start_col] < 0); 
} 

void print_shortest_path() 
{ 
int i,j,new_i,new_j,expect_val,k; 
if (maze[start_row][start_col] >= 0) 
{ 
printf("No path!\n"); 
return; 
} 
printf("%d %d\n", start_row+1, start_col+1); 
i = start_row; 
j = start_col; 
for (expect_val = maze[start_row][start_col]+1; expect_val <= -1; expect_val++) 
{ 
for (k = 0; k < 4; k++) 
{ 
new_i = i + dir[k][0]; 
new_j = j + dir[k][1]; 
if (new_i >= 0 && new_i < m && new_j >= 0 && new_j < n && maze[new_i][new_j] == expect_val) 
{ 
i = new_i; 
j = new_j; 
printf("%d %d\n", i+1,j+1); 
break; 
} 
} 
} 
} 

int main() 
{ 
read_maze(); 
if (find_shortest_path()) 
{ 
print_shortest_path(); 
} 
else 
{ 
printf("No path!\n"); 
} 
return 0; 
}