字符串操作：

http://www.myexception.cn/mobile/455287.html

1,判断两字符串是否相同

NSString *str1 = @"hello pepe";    NSString *str2=[NSString stringWithFormat:@"hello %s","pepe"];   if([str1 isEqualToString:str2]){        NSLog(@"相同");    }    else{        NSLog(@"不同");   } 2,浮点型运算

  CGRect screenRect=[UIScreenmainScreen].bounds;

CGFloat widthf= (screenRect.size.height-self.adView.frame.size.width)/2;

CGFloat heighf=screenRect.size.width-self.adView.frame.size.height-50.0f;