Objective C －2 - 随机数，可变字符串，字符串，SubString

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int
main(int
argc, const
char * argv[])

{

    @autoreleasepool
{

        NSString
*outputString = @"[email protected]#$%^&*()";

        NSMutableString
*resultString = [[NSMutableString
alloc] init];

        NSLog(@"%d", (int)outputString.length);

        for(int
j=0;j<outputString.length;j++)

        {

            NSLog(@"Index = %d  Char = %@",j, [outputString substringWithRange:NSMakeRange(j, 1)]);

        }

        for(int
i=0;i<20;i++)

        {

            int
index  = arc4random() % outputString.length;

            NSString
*indexString = [outputString substringWithRange:NSMakeRange(index, 1)];

            [resultString appendFormat:@"%d %@ ", index, indexString];

        }

        if
(resultString) {

            NSLog(@"%@", resultString);

        }

        return
0;

    }

}