我试图显示以下输出(I am trying to display the following output)

 我试着得到这样的输出： 
 
A
BA
ABA
BABA
ABA
BA
A
 
 但相反，我得到了这个： 
 
AB
ABA
ABAB
ABABA
ABABAB
 
 这就是我曾经尝试过的，而且我完全没想到了。 
 
NSString *strA = @"A";
NSString *strB = @"B";

// Capacity does not limit the length, it's just an initial capacity
NSMutableString *result = [NSMutableString stringWithCapacity:[strA length] * 10];

for (int i = 0; i <= 4; i++)
{
    [result appendString:strA];
    [result appendString:strB];
    NSLog(@"%@", result);
}

I am try to get a output like this:
 
A
BA
ABA
BABA
ABA
BA
A
 
But instead I get this:
 
AB
ABA
ABAB
ABABA
ABABAB
 
This is what i had tried, and i am totally run out of idea.
 
NSString *strA = @"A";
NSString *strB = @"B";

// Capacity does not limit the length, it's just an initial capacity
NSMutableString *result = [NSMutableString stringWithCapacity:[strA length] * 10];

for (int i = 0; i <= 4; i++)
{
    [result appendString:strA];
    [result appendString:strB];
    NSLog(@"%@", result);
}

原文：https://stackoverflow.com/questions/31687480