View Compilation Error

0_0_16316814_12649.cpp: In function 'void BFS()':
0_0_16316814_12649.cpp:20:12: error: 'dx' was not declared in this scope
     if(sx==dx&&sy==dy)//首先判断
            ^
0_0_16316814_12649.cpp:20:20: error: 'dy' was not declared in this scope
     if(sx==dx&&sy==dy)//首先判断
                    ^
0_0_16316814_12649.cpp:40:24: error: 'dx' was not declared in this scope
                 if(tx==dx&&ty==dy)//找到
                        ^
0_0_16316814_12649.cpp:40:32: error: 'dy' was not declared in this scope
                 if(tx==dx&&ty==dy)//找到
                                ^
0_0_16316814_12649.cpp: In function 'int main()':
0_0_16316814_12649.cpp:95:28: error: 'dx' was not declared in this scope
                     if(tx==dx&&ty==dy)
                            ^
0_0_16316814_12649.cpp:95:36: error: 'dy' was not declared in this scope
                     if(tx==dx&&ty==dy)
                                    ^