you give m x n integer array grid gridij be1 represent start square there exactly start square2 represent end square there exactly end square0 represent square walk over1 represent obstacle walk overreturn number 4directional walk start square end square walk nonobstacle square exactly Example 1input grid 100000000021output 2explanation we follow path 1 00010203131211102021222 0010202111010203131222example 2input grid 100000000002output 4explanation we follow path 1 0001020313121110202122232 0001111020212212020313233 0010202122121101020313234 001020211101020313122223example 3input grid 0120output 0explanation there path walk square exactly oncenote start end square grid Constraintsm gridlengthn gridilength1 m n 201 m n 201 gridij 2There exactly start cell end cell