Backtracking คืออะไร?

 ():
    result = []
     ():
          remaining:              
            result.append(path[:])
            
         i  ((remaining)):
            path.append(remaining[i])              
            backtrack(path, remaining[:i] + remaining[i+:])  
            path.pop()                             
    backtrack([], nums)
     result

permutations([, , ])