初级程序员经典面试题 NSDictionary字典类型的错误经典实例

入门级ios程序员 常犯的错误之一：

              13.下面程序段的输出结果是(     B           )。                                                                                                                                                                                                 

              NSMutableDictionary *dic = [[NSMutableDictionary alloc]               initWithObjectsAndKeys:@"1",@"2",@"1",@"3",@"1",@"4",nil];

              NSArray *arr1 =[[NSArray alloc] initWithArray:[dic allKeys]];

              NSArray *arr2 =[[NSArray alloc] initWithArray:[dic allValues]];

              NSMutableDictionary*dic2 = [[NSMutableDictionary alloc] initWithObjects:arr1 forKeys:arr2];

              NSLog(@"%@",dic2);

 

              A.1=2 1=3 1=4

              B.2=1 3=1 4=1

              C. 1=4//字典是顺序执行的第一次 key=1 value=2第二次key=1 value=3（由于key值相同所以覆盖value值）第三次 key=1 value=4  （再次覆盖所以得最终结果key=1 value=4）

              D.4=1